Views: 0 Author: Site Editor Publish Time: 2025-10-15 Origin: Site
In the process of developing micro devices, engineers often face a troubling technical problem: the carefully selected N20 DC motor has insufficient torque output in actual testing, resulting in the device being unable to drive the load normally. This phenomenon of "small horses pulling big cars" not only affects product performance, but may also trigger chain quality problems. When simple N20 motors cannot meet the demand, micro deceleration stepper motors are becoming a highly competitive technological alternative in heavy-duty micro devices.
The torque output of N20 DC motor is essentially limited by its physical size and electromagnetic design. According to the motor torque formula T=Kt × I (where Kt is the torque constant and I is the current), to increase the torque within a finite volume, it can only be achieved by increasing the current or increasing the magnetic flux density, which is limited by temperature rise and material saturation.
operating condition
| Typical N20 motor (6V) | actual requirements
| gap analysis
|
no-load speed
| 8000-10000 RPM | - | - |
Locked-rotor torque
| 15-20 mN·m | - | - |
Rated working point torque
| 5-8 mN·m | 15-30 mN·m | Serious deficiency
|
Continuous working current
| 100-150 mA | 300-500 mA | Oversized operation
|
Slow startup acceleration, unable to quickly reach the target speed
When encountering resistance, the speed drops sharply or even stops running
Under continuous heavy load, the temperature rise is too high, leading to further deterioration of performance
Significantly shortened lifespan, premature wear of brushes and commutators
Unlike DC motors that generate continuous rotation through electromagnetic induction, stepper motors are based on pulse control, which drives the permanent magnet rotor to rotate at a fixed angle by sequentially energizing the stator winding. This discrete control mechanism endows it with unique performance advantages.
feature | N20 motor (6V) | Micro stepper motor |
Low speed torque | Low,dependent on gearbox | Low, dependent on gearbox |
control accuracy | Need encoder feedback | Open loop precise positioning, no cumulative error
|
Response characteristics | There is a delay and the time needs to be accelerated
| Instantaneous start stop, fast response
|
overload capacity
| Easy to block and damage
| Strong short-term overload capacity
|
system complexity
| Simple but with limited accuracy
| Need driver but flexible control
|
Example of torque density comparison
Taking the NEMA 8 series miniature stepper motor as an example, when paired with a 10:1 planetary gearbox:
Output torque: up to 150-400 mN · m
Torque increase: 8-15 times higher than direct drive
Speed range: 100-600 RPM (suitable for most precision equipment)
Interface adaptation considerations
Installation hole matching: NEMA 8 standard installation hole spacing is 20mm, equipment structure needs to be evaluated
Axis diameter and connection: Stepper motors typically have a 4mm or 5mm optical axis, which needs to be converted to the 3mm D-axis of N20
Dimensions: Stepper motors are usually longer and require verification of spatial constraints
Optimal configuration plan
plaintext
Micro stepper motor → planetary gearbox → torque sensor → load
↓
Microstep driver ← Motion controller ← Position feedback (optional)
Key parameter calculation
Required torque=Load torque x Safety factor (1.5-2.0)
Reduction ratio selection=rated speed of stepper motor/target output speed
Driver current=Stepper motor phase current x Microstep subdivision coefficient
Original plan: N20 motor+encoder feedback, positioning accuracy ± 0.5mm
Problem: Unstable positioning and slow response speed when load changes
Alternative solution: NEMA 8-stepper motor+5:1 reducer
Improvement effect: The positioning accuracy has been improved to ± 0.05mm, and the response time has been reduced by 60%
Original plan: N20 motor-driven peristaltic pump, flow control accuracy ± 8%
Problem: Unstable flow rate during pressure fluctuations, long-term performance degradation
Alternative solution: 17mm diameter micro stepper motor directly driven
Improvement effect: Flow control accuracy increased to ± 2%, lifespan extended by 3 times
Case Three: Robot Joint Drive
Original plan: N20 motor+multi-stage gearbox, large volume, obvious backlash
Problem: Significant joint shaking and poor repeatability in positioning
Alternative solution: Micro stepper motor+single-stage planetary gearbox
Improvement effect: The backlash has been reduced to within 10 arc minutes, and the smoothness of operation has been significantly improved
Cost Project N20 DC Motor Solution Micro Stepper Motor Solution
Motor cost $1.5-3 $8-15
Driver circuit $0.5-1 (H-bridge) $3-5 (stepper driver)
Sensor $2-4 (encoder) $0-2 (optional encoder)
Total cost $4-8 $11-22
Reliability cost: The stepper motor has no brush wear, reducing the failure rate by 50-70% during its lifespan
Maintenance cost: Maintenance free design reduces after-sales service demand
Performance cost: Higher precision and stability enhance the competitiveness of end products
Although the initial investment for the stepper motor scheme is relatively high, it has significant advantages in the following scenarios:
Batch production equipment: reliability improvement reduces after-sales maintenance costs
High precision applications: Performance improvement brings product premium capability
Long lifespan requirement: reduce replacement and maintenance frequency
Prototype validation phase: Purchase samples for performance comparison testing
Small batch trial: Install verification on representative devices
Design optimization: Optimize mechanical and electrical interfaces based on test results
Comprehensive switch: Batch replacement after completing all verifications
Retain the installation interface of N20 motor and adapt it to the new motor through an adapter board
Reserve the current margin required for the stepper driver in the power system
Reserved step pulse control interface for control software
Closed loop stepper motor: combining high torque of stepper motor and high reliability of servo motor
Integrated solution: motor+driver+controller integrated design
Application of new materials: amorphous stator, high-temperature permanent magnet to enhance power density
The price of micro stepper motors is decreasing at a rate of 8-12% per year
The localization process is accelerating, and the cost-effectiveness continues to improve
Specialized driver chips reduce costs and simplify circuit design
Faced with the technical bottleneck of insufficient torque of N20 motor, micro deceleration stepper motor provides a practical and feasible alternative solution. Although the initial cost is high, its advantages in accuracy, reliability, and torque density make it irreplaceable in heavy-duty micro devices.
Decision suggestion:
For applications that do not require high precision and are extremely cost sensitive, optimizing the N20 motor usage plan can be attempted
For scenarios with high reliability requirements and large load changes, it is strongly recommended to use a micro stepper motor solution
During the transition period between new and old technologies, compatibility design is adopted to reserve space for future upgrades
Technology selection is never simply a price comparison, but a comprehensive consideration based on the full lifecycle cost. When your device is facing the problem of insufficient torque, turning to the micro stepper motor technology route may be a key decision to break the performance bottleneck and enhance product competitiveness.
