A Gearbox (also known as a speed reducer or gear reducer) is a mechanical device used to transmit and transform motion. The primary function of a gearbox is to reduce the rotational speed of the motor while simultaneously increasing the output torque, enabling machinery to operate more powerfully and efficiently.
A gearbox is often combined with an electric motor to form a geared motor, which helps ensure stable operation, saves energy, and extends the system’s lifespan, making it suitable for a wide range of industrial and civil applications.
Structure of a Gearbox
A gearbox is a mechanical drive component composed of many cooperating parts designed to reduce rotational speed while simultaneously increasing torque. Below is a detailed breakdown of its structure:
Gear train: Consists of spur, helical, or bevel gears, arranged in multiple stages (1-stage, 2-stage, 3-stage, etc.). The number of gears typically ranges from a few to a dozen, depending on the design. This assembly performs the tasks of speed reduction and transmission ratio conversion, while transmitting torque from the input shaft to the output shaft. The gears are precisely machined for smooth meshing, reducing noise and power loss.
Input & output shafts: The input shaft receives motion from the motor (which can be connected via couplings, V-belts, or chains), typically a tapered or straight shaft depending on the type. The output shaft transmits the reduced torque to the load mechanism (conveyors, cranes, presses, etc.). The material and machining of the shafts ensure good resistance to bending and torsion.
Bearings and bearing housings: Bearings and supports absorb forces for the shafts and gears, maintaining precise shaft centerline positioning, reducing friction and wear. Selecting the appropriate bearing type helps extend lifespan and ensure stable operation.
Housing / casing: The housing is usually made of cast iron, steel, or aluminum alloy (for smaller gearboxes), capable of withstanding forces, dissipating heat, and protecting internal components. The housing is designed with reinforcing ribs, oil channels, inspection covers, and bolt holes to secure the unit to the machine frame.
Fastening system & screws: Bolts, screws, keys, and seals secure components, seal joints, and ensure precise assembly. Keys transmit torque between the shaft and gears or pulleys.
Gaskets, seals, and washers: Rubber gaskets, oil seals, and various washers help prevent oil leakage, block dust and water ingress, reduce friction, and protect bearings and gears from contamination.
Lubrication system (oil/grease): Includes oil channels, pumps (if applicable), oil/grease fill points, and drain plugs. Proper and sufficient lubrication helps cool, reduce friction, prevent wear, and extend the lifespan of the drive system.
Inspection covers and maintenance ports: Covers or openings on the housing allow for inspection, maintenance, oil changes, and component replacement without having to dismantle the entire gearbox.
Breather / vent plug: A device that prevents pressure buildup within the housing due to temperature changes, helping to prevent water and dust ingress while balancing internal pressure.
Flanges, pulleys, couplings, and auxiliary drives: Depending on the application, a gearbox can integrate an output flange, pulley, external gear, or coupling for direct connection to the load or via V-belt or chain drives. These components ensure a secure, torque-resistant connection.
Gearbox Classification
Classification by Product Type
- NMRV Gearbox: A popular type with a compact, lightweight design and high efficiency. Widely used in conveyor belts, packaging machines, and automation systems.
- Cycloid Gearbox: Uses unique cycloid gears, capable of handling heavy loads and operating smoothly. Suitable for industrial machinery requiring high precision.
- ZQ Gearbox: Also known as ZQ or ZQ gearbox, designed for heavy-duty applications with high durability, commonly used in mining, cement, and steel production.
- Worm Gearbox: Operates stably, capable of significant speed reduction in a small space. Often used in lifting machines, cranes, and systems requiring high torque.
- Screw Jack Gearbox: Specifically designed to convert rotary motion into linear motion, applied in CNC machines, presses, and automation systems.
- Mechanical Variator: Designed to adjust speed during operation without stopping the machine. Suitable for production lines that require continuous speed changes.
- HB Heavy-Duty Gearbox, T Bevel Gearbox: These are high-power drive units, specifically designed to reduce rotational speed and increase torque, meeting the requirements for durable and heavy-load operation in heavy industries.
- F Parallel Shaft Heavy-Duty Gearbox: Output shaft designed parallel to the input shaft. Compact structure, easy to install in limited spaces. Used in conveyors, mixers, and industrial drive systems.
- R Helical In-line Heavy-Duty Gearbox: Output shaft is in-line with the input shaft, direct drive. Designed for harsh operating conditions. Used in construction machinery, crushers, and large-load systems.
- K Right-Angle Heavy-Duty Gearbox: Output shaft is perpendicular to the input shaft, using spiral bevel gears. High precision, high transmission efficiency. Used in production lines, lifting equipment, and conveyors.
- S Worm-Helical Right-Angle Heavy-Duty Gearbox: Output shaft is perpendicular to the input shaft, combining helical gears and a worm shaft. High efficiency, high torque. Used in cranes, elevators, and heavy transport systems.
Classification by Number of Stages
- 1-Stage Gearbox
A 1-Stage Gearbox is a type of gearbox that includes only one pair of meshing gears, suitable for systems that do not require an extremely high transmission ratio. The outstanding advantages of this type are its simple structure, easy installation, and low investment cost.
Some popular 1-stage gearboxes on the market include:
- NMRV 1-Stage Gearbox: uses a worm gear, compact, lightweight, often used in small drive systems.
- Worm Gearbox 1-Stage Gearbox: designed for stable transmission, smooth operation.
- Screw Jack Gearbox 1-Stage Gearbox: suitable for moderate lifting applications.
- Cycloid Gearbox 1-Stage Gearbox: high durability, high torque, often used in automated production lines.
- ZQ 1-Stage Gearbox: a common type with stable working performance and reasonable cost.
- 1-Stage Mechanical Variator: supports simple mechanical speed adjustment, suitable for light-load machines.
- HB Heavy-Duty 1-Stage Gearbox: specifically for heavy-duty transmission, powerful and durable operation.
- F Parallel Shaft Heavy-Duty 1-Stage Gearbox: efficient transmission in limited spaces.
- K Right-Angle Heavy-Duty 1-Stage Gearbox: right-angle output shaft design, suitable for specific installation spaces.
- S Worm-Helical Right-Angle Heavy-Duty 1-Stage Gearbox: compact, precise power transmission for heavy industrial systems.
- R Helical In-line Heavy-Duty 1-Stage Gearbox: commonly used in mechanical applications, conveyors, industrial screw conveyors.
- 2-Stage Gearbox
A 2-Stage Gearbox is a type of drive unit consisting of two pairs of meshing gears, which helps to increase the transmission ratio compared to the 1-stage type. Thanks to its better torque transmission capability, this type of gearbox is often used in mechanical systems requiring medium loads and slower rotational speeds.
Common 2-stage gearboxes currently include:
- Cycloid Gearbox 2-Stage Gearbox: Enhanced transmission ratio, stable operation in continuous working environments.
- ZQ 2-Stage Gearbox: Often used in industrial machinery systems requiring high durability.
- 2-Stage Mechanical Variator: Supports more precise speed adjustment, suitable for applications requiring flexible speed changes.
- HB Heavy-Duty 2-Stage Gearbox: High load capacity, durable operation in heavy-load environments.
- F Parallel Shaft Heavy-Duty 2-Stage Gearbox: Compact design, suitable for installation in tight spaces with high transmission efficiency.
- K Right-Angle Heavy-Duty 2-Stage Gearbox: Space-optimized, high transmission ratio, suitable for complex mechanical systems.
- S Worm-Helical Right-Angle Heavy-Duty 2-Stage Gearbox: Efficient power transmission, smooth operation, used in many heavy industrial production lines.
- R Helical In-line Heavy-Duty 2-Stage Gearbox: Robust design, stable operation in drive applications requiring high torque.
- 3-Stage Gearbox
A 3-Stage Gearbox is a type of drive unit consisting of 3 pairs of meshing gears, which helps to achieve an extremely large transmission ratio. Due to its ability to reduce rotational speed to very low levels while maintaining high torque, this type of gearbox is used in mechanical systems requiring slow and stable drives, such as crushers, large conveyors, or specialized production lines. A 3-Stage Gearbox can also be found as a 3-stage mechanical variator, an effective solution for flexibly adjusting motor speed.
Advantages of a Gearbox
The gearbox is an indispensable mechanical drive component in today’s industrial machinery systems. Thanks to its outstanding characteristics in terms of efficiency and durability, this device is increasingly widely used in many fields. Here are the notable advantages of a gearbox that you should know:
- Compact design, easy to install: A gearbox has a compact structure, easily installed in limited spaces without taking up much room. Suitable for both new systems and for replacing or upgrading old equipment.
- Simple structure, easy to maintain: Thanks to its reasonable mechanical design, users can easily clean, lubricate periodically, or replace components when needed without much time.
- Diverse power capacities and transmission ratios: A gearbox is manufactured with various power ranges, sizes, and transmission ratios, suitable for all needs from light, medium to heavy loads in industry.
- Effective speed reduction and torque increase: This is the main function of a gearbox, helping the motor work stably, save energy, and ensure high pulling force and transmission efficiency.
- Smooth operation, low noise: Precisely machined gears mesh smoothly, reducing vibration and noise during operation, providing a smooth and workplace-friendly experience.
- High durability, long lifespan: The housing and internal components are usually made of steel, cast iron, or high-strength alloys, ensuring durable operation in harsh environments.
- Reasonable cost, economical: Compared to many other complex drive systems, a gearbox is relatively inexpensive, highly durable, and rarely breaks down - helping to save long-term investment and maintenance costs.
- Flexible application: A gearbox can be combined with various electric motors, conveyors, cranes, presses, stirrers, lifting equipment, etc., suitable for all industries from industrial manufacturing to agriculture and construction.
Thanks to the above outstanding advantages, the gearbox is always a top choice for increasing efficiency, reducing operating costs, and extending the lifespan of the entire drive system.
Gearbox Installation Guide
Preparation before Installation
- Check the product: Ensure the gearbox is not damaged or deformed during transport; check for complete accessories, oil/grease, and covers.
- Clean the installation area: The floor, machine frame, support, or base must be flat, sturdy, free of oil/grease, and free from vibration.
- Check shaft and coupling dimensions: Ensure the motor shaft and the input - output shafts of the gearbox have appropriate dimensions, keyways, and lengths for assembly.
Choosing an Installation Location
- Select a sturdy, fixed position: The gearbox should be installed in a dry, well-ventilated area, easy to maintain, and away from heat sources or moisture.
- Determine the installation orientation: Depending on the design type (horizontal shaft, vertical shaft, right-angle shaft, etc.), it must be positioned correctly to ensure effective lubrication.
- Ensure alignment: The shaft of the electric motor and the input shaft of the gearbox must be concentric, avoiding misalignment that can cause rapid wear of bearings and gears.
Assembling the Drive Shaft
- Connect to the electric motor: Install the coupling or pulley between the motor shaft and the input shaft of the gearbox. If using V-belts or chains, adjust the tension appropriately to avoid slipping or overloading.
- Install the output shaft: The output shaft can be connected to the load via a flexible coupling, gear, chain, or pulley. When installing couplings, it is advisable to choose one with damping to absorb vibrations and protect gears and bearings from mechanical impact.
Securing the Device
- Use bolts, washers, and nuts to tighten the gearbox to the base or machine frame.
- Tighten nuts evenly in a diagonal pattern to prevent housing deformation.
- Ensure all bolts are tightened with sufficient and uniform force, helping the gearbox remain stable during operation.
Final Check and Adjustment
- Manually rotate the output shaft to check for smooth movement, no jamming or vibration.
- Fill with lubricating oil according to the recommended capacity and type specified in the manufacturer’s instructions.
- Check oil seals, oil fill cap, oil drain plug, and washers to prevent leakage.
Trial Run and Acceptance
- No-load run: Operate the gearbox for 15-30 minutes to check for noise, vibration, and housing temperature.
- Light-load run: Once stable, gradually increase the load to the rated capacity.
- Monitor parameters: If abnormal noises, high temperatures, or oil leakage are detected, stop the machine for immediate inspection.
Post-Installation Maintenance
- After the first 100-200 hours of operation, the lubricating oil should be changed to remove metallic debris generated during the break-in period.
- Regularly check bolt tightness, oil level, seal condition, and concentricity between shafts.
