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Small dc gear motors generally refer to gear motors with a power of less than 100 watts (W) and a dc voltage of 3V-48V. Small dc gear motor is widely used in transmission systems that require precise control and high efficiency due to its small size and high torque.
SGMADA is a leading small dc gear manufacturer in China. This article will deeply analyze the working principle of SGMADA’s small DC gear motors and provide a detailed selection guide to help our customers make the best choice in the transmission field.
1.Baisc knowledge of Small DC Gear Motor
1.1 What is a Small DC Gear Motor
Small DC gear motor is a mechanical device that combines a DC motor and a gearbox. This motor adjusts the output speed and torque of the motor end through gear transmission deceleration, thereby meeting the power requirements of small size, high torque, and low speed required in the field of micro transmission.
1.2 Components of DC Gear Motor
The dc gear motor consists of 2 core parts – DC motor and Gearbox.
- DC Motor （Power Source）：A DC motor generates a magnetic field through electric current, driving the rotor to rotate, thereby converting electrical energy into mechanical energy.
- Gearbox （Gear strcuture）：The gearbox reduces the speed of the motor input through internal gear transmission and outputs higher torque.
2.Working Principle of Small DC Gear Motor
2.1 Working Principle of DC Motor
A DC motor is an electric motor that converts direct current electrical energy into mechanical energy. It drives the rotor to rotate and generates mechanical motion through the action of current in a magnetic field.
I. Generating the Magnetic Field
When the DC power is connected, current flows through the brushes and commutator into the armature coil, creating an electromagnetic field.
II. Electromagnetic Force
According to electromagnetic principles, a current-carrying conductor in a magnetic field experiences a force. The stator’s constant magnetic field interacts with the armature’s electromagnetic field, producing a torque.
III. Current Commutation
As the rotor turns, the commutator changes the point of contact with the brushes, reversing the direction of the current in the armature coil. This aligns the current with the stator’s magnetic field, ensuring that the rotor continues to rotate.
IV. Continuous Rotation
Since the commutator continuously changes the direction of the current in the armature coil, the electromagnetic force always keeps driving the rotor in one direction. As long as there is a DC power supply, the rotor will continue to rotate, converting DC power into mechanical energy output.
2.2 Working Principle of Gearbox
The gearbox is a mechanical structure designed based on the principle of gear transmission. Its main function is to reduce the speed of the motor input end and increase the output torque.
Why we choose gearboxes?
| Gearbox Function | Description |
|---|---|
| 1. Reduce speed and increase torque | Reduces motor speed while increasing torque |
| 2. Load Matching | Optimizes motor performance by matching it to high load requirements. |
| 3. Increase Starting Torque | Boosts starting torque to handle heavier loads from a standstill. |
| 4. Motion Direction | Changes the direction of the output shaft’s motion to meet design requirements. |
| 5. Reduce Costs | Uses smaller, cost-effective motors to achieve desired performance, lowering system costs. |
Types of gear transmission in gearbox
Gearboxes transmit power through the meshing of gears. Gear transmission can be divided into different types according to the shape and meshing method of the gears.
Spur Gear Drive
Spur gear transmission is the most basic gear transmission structure. Since the axes of the two gears in the spur gear transmission system are parallel, and this parallel configuration can achieve efficient and stable power transmission, it is called parallel shaft transmission.
| Advantages | Disadvantages |
|---|---|
| Simple design | Low efficiency |
| Low cost | Noisy at high speeds |
| Easy to maintain | Wears quickly, shorter lifespan |
| High reliability | Not suitable for high load or impact load applications |
Planetary Gear Drive
Planetary gear transmission is a highly efficient gear structure. It consists of a sun gear, multiple planetary gears, a planet carrier and an inner gear ring, in which the planetary gears revolve around the sun gear and mesh with the inner gear ring.
| Advantages | Disadvantages |
|---|---|
| High efficiency | High production cost |
| High torque density | Difficult to repair and change |
| Low Noise | Complex design |
| High precision | Fixed shaft output – center shaft output |
Worm Gear Drive
The worm gear drive consists of a spiral worm and a meshing worm wheel. It can achieve high reduction ratio and self-locking function, and is suitable for applications that need to prevent reverse motion.
| Advantages | Disadvantages |
|---|---|
| High Gear Ratio | Low efficiency |
| Self-Locking | High machining costs for worm |
| Low Noise | Easy to wear |
| 90° output shaft | Low accuracy |
3.How to Select Small DC Gear Motor
Selecting the right gear motor is crucial for ensuring the efficient, stable, and reliable operation of a transmission system. Thus, choosing a gear motor is a key consideration for engineers when designing such systems. SGMADA will share the key points for choosing a small gear motor through detailed parameter explanations.
3.1 Choose the right motor working point
The motor’s working point is the first important parameter to consider when selecting a motor. The motor’s working point means the output torque and speed that the motor outputs when it is operating normally in this system.
As can be seen from the graph, the motor speed decreases as the torque increases, but the relationship between the two is not a linear one.
When selecting a motor, sgmada will provide the motor’s load curve to help customers choose the appropriate motor operating point.
When the motor does not operate within the curve range, it means that the motor is overloaded, which will cause some adverse effects.
| Effect | Cause | Consequence |
|---|---|---|
| Overheating | Load or speed exceeds design limits | Motor damage or failure |
| Efficiency Drop | Operating at non-optimal points | Energy waste, increased cooling needs |
| Mechanical Wear | Bearings and gears under excessive stress | Shortened lifespan, higher maintenance costs |
| Vibration and Noise | Operating in unstable range | Reduced operation quality, potential structural damage |
| Frequent Protection Triggers | Overload protection devices activating frequently | Increased downtime, reduced production efficiency |
3.2 Choose the right motor type
According to the needs, the micro gear motor can be combined with different motor types. The following are several commonly used types of motors.
| Motor Type | Features | Typical Applications | Price |
|---|---|---|---|
| DC Motor | Simple structure, Brush | robots, household appliances | Low |
| BLDC Motor | High efficiency, long lifespan | Electric vehicles, drones, precision instruments | High |
| Stepper Motor | Precise position control, fast response, suitable for open-loop control | 3D printers, CNC machines, camera gimbals | Medium |
| AC Motor | Robust structure, simple maintenance | Small household appliances, office equipment | Low |
3.3 Choose the right gearbox type
The selection of the gearbox needs to select the appropriate internal gear structure according to the characteristics of the gear transmission
| Gearbox Type | Features | Typical Applications | Price Range |
|---|---|---|---|
| Spur Gearbox | Simple design, low cost | low-speed machinery,robot | Low |
| Planetary Gearbox | Compact design, high torque density, | Robotics, aerospace, precision instruments | High |
| Worm Gearbox | High gear ratios, self-locking, 90° output shaft | Smart Home, Industry | Medium |
3.4 Choose the right gear material type
Gear material directly affects the load capacity and noise level of the gearbox. According to the different gear materials and processing technology, we divide gear materials into the following categories.
| Gear Material | Features | Selection Criteria |
|---|---|---|
| Cut Steel Gears | High strength, durability, wear resistance | High load, high precision applications |
| Powder Metallurgy Gears | Good wear resistance, complex shapes, cost-effective | Medium load, cost-sensitive applications |
| Plastic Gears | Lightweight, low cost, quiet operation | Low load, noise reduction, corrosion resistance |
3.5 Choose the output shaft
The motor output shaft is one of the core components of the motor. Its main function is to transmit the mechanical energy generated by the motor, providing rotational kinetic energy. The output shaft needs to withstand radial and axial loads, ensuring the stable operation of the motor and mechanical system. Additionally, the output shaft is used to connect and secure gears, couplings, and other transmission components through bearing support.
Based on function and shape, SGMADA can process the following types of output shafts. We also accept custom orders and can evaluate your drawings to determine if we can manufacture special output shafts.
| Output Shaft Type | Features | Selection Criteria |
|---|---|---|
| Round Shaft | Smooth | Flexible connections, commonly used with clamps, sleeves, or couplings |
| Keyed Shaft | Keyway to prevent slipping | Reliable torque transmission for gears, pulleys, and couplings |
| Splined Shaft | Multiple longitudinal grooves | High torque applications |
| Threaded Shaft | Flexible connections | applications requiring anti-rotation |
| D-Shaped Shaft | Partially flat surface to prevent slipping | Small motors, toy motors, applications requiring anti-rotation |
| Double D Shaft | Two flat surfaces forming a double D shape | Higher torque resistance |
3.6 Choose the suitable accessories for your application
SGMADA can provide the following accessories for gear motors based on customer needs. We offer a wide range of high-quality accessories to ensure optimal performance and reliability for your specific applications.
| Accessory Type | Function | Application Scenarios |
|---|---|---|
| Encoder | Provides position and speed feedback | Robotics, automation equipment |
| Brake | Stops or holds motor position | Elevators, cranes |
| Coupling | Connects motor shaft and load shaft, transmits torque | Different shaft diameters and alignment requirements |
| Sensor | Monitors motor operating conditions | Real-time monitoring and motor protection |
| Heat Sink | Helps dissipate heat, prevents motor overheating | High-power motors, long-duration operations |
| Cables and Connectors | Connects motor to controllers and power supply | Ensures reliable and safe electrical connections |
4.Small DC Gear Motor Selection: Critical Parameters
When selecting a DC gear motor, engineers should consider several key electrical parameters. These parameters not only optimize the motor’s performance within the system but also ensure its reliability. SGMADA needs to understand these key parameters to provide you with the best motor selection and design solutions.
4.1 Size – Dimension
1. Appropriateness of Motor Size
• Importance: The overall dimensions of the motor must fit within the installation space of the equipment, including length, width, and height.
• Explanation: Appropriate sizing ensures the motor can be smoothly installed within the equipment or system without interfering with the normal operation of other components.
2. Mounting Hole Compatibility
• Importance: The position and size of the mounting holes must match the mounting points on the equipment.
• Explanation: If the mounting holes’ position or size does not match, the motor may not be securely fixed, potentially leading to instability and compromising the system’s stability and safety.
3. Output Shaft Position and Connection
• Importance: The output shaft of the motor is crucial for connecting the motor to other parts of the system.
• Explanation: The position of the output shaft must reliably align with the load or driven components to ensure effective power transmission. The shaft type (such as round, keyed, splined, etc.) also determines the choice of couplings or other connection methods.
4. Motor Weight
• Importance: The weight of the motor is an important factor, especially in mobile applications or systems where reducing total weight is crucial.
• Explanation: Heavier motors may increase the structural burden, potentially affecting the performance and efficiency of the equipment. Lightweight design is particularly important in these cases to optimize overall system performance.
4.2 Motor Voltage
• Voltage Definition: Motor voltage refers to the rated voltage at which the motor is designed to operate, expressed in volts (V).
Selecting the suitable motor voltage is crucial to ensure the motor works efficiently and safely. The appropriate voltage affects not only the starting and running characteristics of the motor but also its efficiency, power consumption, and lifespan.
| Voltage Range | Power Supply | Application Areas |
|---|---|---|
| 3V – 6V DC | Batteries (e.g., AA, AAA) | Portable electronic devices, battery-powered toys |
| 12V – 24V DC | Lithium battery packs，Batteries | Robots, household appliances, automotive electronics |
| 48V DC | Lithium battery packs | Electric bicycles, electric scooters, power tools |
| 230V AC | Household power outlets, industrial power supplies | Household appliances, HVAC systems |
4.3 Motor Current
• Current Definition: Motor current refers to the amount of electrical current flowing through the motor’s windings, measured in amperes (A).
Selecting the appropriate motor current is crucial for the efficient and safe operation of the motor. The right current affects not only the starting and running conditions but also the motor’s torque output, power consumption, and thermal management.
| Current | Definition |
|---|---|
| Starting Current | The high current when the motor starts, affecting starting torque and time. |
| Rated Current | The standard operating current under rated load, ensuring optimal performance. |
| Stall Current | The maximum current when the motor rotor is locked, preventing motor damage. |
| Motor Losses | Energy losses caused by current, including copper and iron losses. |
| Thermal Management | Managing heat generated during operation to prevent motor overheating. |
4.4 Motor Power
• Power Definition: Motor power refers to the total electrical power consumed by the motor, measured in watts (W).
Selecting the appropriate motor power is crucial for the efficient and safe operation of the motor. Motor power includes input power ( P_{in} ), output power ( P_{out} ), and loss power ( P_{loss} ), which represent the total energy supplied, the useful mechanical energy output, and the energy lost as heat and other inefficiencies, respectively.
| Power Type | Symbol | Definition |
|---|---|---|
| Input Power | ( P_{in} ) | The total electrical energy absorbed by the motor from the power source. |
| Output Power | ( P_{out} ) | The effective power converted into mechanical energy by the motor and delivered to the load. |
| Loss Power | ( P_{loss} ) | The energy lost within the motor due to resistance, friction, heat, and other factors. |
4.5 Motor RPM
• RPM Definition: Motor RPM (Revolutions Per Minute) refers to the number of complete turns the motor’s rotor makes in one minute. It is a critical parameter that defines the speed of the motor’s output shaft.
With the use of a gear system, gear motors provide low RPM with high torque mechanical output. SGMADA can customize the RPM range based on different gear ratios to meet specific application requirements. This ensures the motor delivers the optimal RPM and performance for the system, preventing overheating and mechanical failures due to inappropriate speeds.
| RPM Type | Definition |
|---|---|
| No-Load Speed | The maximum speed at which the motor runs without any load, representing the upper limit of the motor’s speed capability. |
| Rated RPM | The speed at which the motor operates under normal load conditions, ensuring optimal performance. |
| Stall RPM | The speed at which the motor’s rotor stops turning due to excessive load or resistance, indicating maximum torque. |
4.6 Motor torque
• Torque Definition: Motor torque refers to the rotational force produced by the motor’s shaft, typically measured in Newton-meters (Nm) or pound-feet (lb-ft).
Motor torque includes stall torque, rated torque, and peak torque. Proper torque selection affects the motor’s efficiency, longevity, and overall performance.
| Torque Type | Symbol | Definition |
|---|---|---|
| Stall Torque | ( \tau_{stall} ) | The maximum torque a motor can produce when the rotor is locked and not rotating. |
| Rated Torque | ( \tau_{rated} ) | The continuous torque a motor can deliver without overheating under normal conditions. |
| Peak Torque | ( \tau_{peak} ) | The maximum torque a motor can deliver for short periods without causing damage. |
4.7 Motor Lifespan
The lifespan of a gear motor is determined by both the lifespan of the gearbox and the motor. According to the “barrel principle,” the overall lifespan of the gear motor is limited by its shortest component lifespan. In other words, if any part of the gearbox or motor fails, the entire gear motor will stop functioning.
• Motor Lifespan: Motor lifespan refers to the total time a motor can operate normally under specific working conditions.
| Factor | Description |
|---|---|
| Design Structure | Brush or Brushless ，Heat dissipation design |
| Operating Environment | Temperature, humidity, dust, and corrosive gases. |
| Material Quality | Bearing， Coil ， Magnet |
| Operating Conditions | Load condition，working condition，speed |
• Gearbox Lifespan: The lifespan of a gearbox refers to the total time it can operate normally while transmitting torque and speed, measured in hours (h).
| Factor | Description |
|---|---|
| Mechanical Load | High loads or shock loads accelerate gear wear. |
| Lubrication | lubrication reduces wear and heat generation. |
| Gear Material | powder metallurgy, cut steel, and engineering plastics. |
| Environmental Conditions | Dust, humidity, and corrosive gases |
4.8 Gear material
In selecting a gear motor, the choice of gear material is a critical consideration as it directly affects the gearbox’s performance, durability, and lifespan.
| Material | Advantages | Disadvantages |
|---|---|---|
| Steel Gears | 1. High precision 2. High strength | 1. Heavy 2. High cost |
| Powder Gears | 1. Low cost 2. Feasibility for complex shapes | 1. Lower strength 2. Poor wear resistance |
| Plastic Gears | 1. Lightweight 2. Low noise | 1. Lower strength 2. Heat sensitive, may deform at high temperatures |
4.9 Motor accessories
Motor accessories can be selected to achieve various functions, which is crucial in motor selection. Accessories such as encoders, brakes, and heat sinks not only meet specific control requirements but also enhance motor efficiency.
| Accessory | Function |
|---|---|
| Encoder | Provides precise position and speed feedback for accurate control and automation applications. |
| Controller | Regulates the motor’s speed, torque, and direction, ensuring optimal operation. |
| Brake | Allows for rapid deceleration or stopping of the motor, providing safety, especially in emergencies. |
| Fan | Assists in cooling, reduces motor temperature, prevents overheating, and extends motor lifespan. |
5. Conclusion
5.1 Future development trends for small dc gear motor
The gear motor market has a promising outlook globally, with the demand for gear motors continually rising due to rapid advancements in industrial automation, smart manufacturing, and electric robotics. In the future, technological advancements will significantly improve gear motor efficiency, reduce size, and lower costs. Additionally, the integration of intelligent control technologies will make gear motors more precise and adaptable, catering to various complex applications.
5.2 Contact SGMADA
At SGMADA, we recognize the critical role that gear motors play in industries such as industrial automation, robotics, and automotive manufacturing. Our expertise in gear motor design and selection ensures that we provide solutions tailored to meet specific requirements for torque, speed, and power. By leveraging our in-depth knowledge and extensive experience, we help our customers optimize their systems’ performance and reliability. At SGMADA, we are committed to delivering high-quality gear motors that enhance the efficiency and lifespan of our clients’ applications.
