What Is the Difference Between Strain Wave & Cycloidal drives

Understanding Cycloidal Gearboxes | Single-stage vs Multi-stage

It's no secret that cycloidal gearboxes are important in mechanical engineering, especially when it comes to precision motion control and efficient power transmission. The gear systems differ from harmonic wave/strain wave gearboxes by using a cycloidal disk and needle bearings to transmit torque with minimum backlash, achieve high reduction ratios, and support substantial loads. 

This blog will talk about single-stage and multi-stage cycloidal gearboxes.

Single-Stage Cycloidal Gearboxes

Single-stage cycloidal gearboxes are compact, high-precision devices designed for applications requiring efficient torque transmission and minimal to zero backlash. These gearboxes operate on the principle of a cycloidal disc rotating eccentrically, engaging with pins or rollers to convert input shaft rotation into a slowed output motion.

Design and Operation

  • Mechanism: At the heart of a single-stage cycloidal gearbox is a cycloidal disc that rotates around an eccentric bearing, engaging with stationary pins on the gearbox housing through rollers. This unique mechanism allows for the efficient transmission of torque with a high reduction ratio in a single stage.
  • Components: Key components include the cycloidal disc, eccentric cam, needle bearings (or rollers), and the output shaft. The compact arrangement of these components contributes to the gearbox's high load-bearing capacity and robustness.

Advantages of Single Stage Cycloidal Gear Boxes

  • High Torque and Low Backlash: The engagement between the cycloidal disc and the pins ensures that high torque can be transmitted with minimal backlash, making these gearboxes ideal for precision applications.
  • Compact Design: Due to the efficient use of space and the high reduction ratios achievable in a single stage, these gearboxes are notably compact, fitting into tight spaces where other types of gearboxes might not.
  • Durability: The rolling contact reduces wear and tear on the components, extending the gearbox's lifespan even in high-load applications.

Typical Applications

  • Robotics: Used in robotic arms and joints where precise control and high torque in a compact form factor are essential.
  • Automated Machinery: Ideal for use in automated production lines where space is limited and equipment reliability is critical.
  • Precision Equipment: Applied in medical devices, aerospace components, and other machinery where precise movement and reliability are paramount.

Single-stage cycloidal gearboxes offer a blend of precision, efficiency, and durability, making them suitable for a wide range of applications where these attributes are in demand. Their design and operational characteristics ensure they remain a preferred choice for engineers and designers looking to optimize performance in compact spaces. 

Single-Stage Cycloidal Gearbox by Sumitomo

Multi-Stage Cycloidal Gearboxes

For applications that require extreme accuracy and control, multi-stage cycloidal gearboxes offer higher reduction ratios and precision than their single-stage counterparts. Through the use of multiple cycloidal discs and pins, these gearboxes are able to transmit and reduce torque across several stages.

Design and Operation

  • Mechanism: Multi-stage cycloidal gearboxes utilize a series of cycloidal discs, each stage designed to further reduce the speed of the input shaft before transmitting it to the output shaft. This staged reduction allows for higher overall reduction ratios than single-stage designs.
  • Components: Similar to single-stage versions, these gearboxes consist of cycloidal discs, eccentric bearings, needle bearings (or rollers), and output shafts. The addition of multiple discs and corresponding pin sets distinguishes the multi-stage design, enabling it to handle higher reduction ratios efficiently.

Advantages of Multi Stage Cycloidal Gear Boxes

  • Higher Reduction Ratios: By employing multiple reduction stages, these gearboxes can achieve extremely high reduction ratios, making them suitable for applications requiring very slow and precise output speeds.
  • Increased Precision and Torque: The multi-stage approach allows for a more significant torque output and enhanced precision, as each stage can be finely tuned to optimize performance.
  • Compact design Maintained: Despite the addition of extra stages, multi-stage cycloidal gearboxes remain relatively compact, thanks to the efficient use of space inherent in cycloidal design principles.

Typical Applications

  • Precision Engineering: Essential in fields requiring ultra-precise movement, such as semiconductor manufacturing and optical equipment.
  • High-Torque Machinery: Beneficial for applications where space is at a premium but high torque and precision are necessary, like in heavy-duty robotic arms or aerospace actuators.
  • Advanced Robotics: Used in sophisticated robotics where control and precision over a wide range of speeds are crucial for performance and functionality.

Multi-stage cycloidal gearboxes' ability to provide high reduction ratios and torque in a compact package makes them invaluable components in many modern, high-precision applications. 

Multi-Stage Cycloidal Gearboxes by Sumitomo

  • Fine Cyclo UA-Series: Double-stage cycloidal gearbox with a planetary 1st stage and cycloidal 2nd stage.
  • Fine Cyclo T-SeriesSpur gear double-stage high-precision cycloidial gear box. It comes pre-staged and has three eccentrics.

Differences and Applications of Each Cycloidal Gearbox Type

When selecting a cycloidal gearbox for a specific application, understanding the differences between single-stage and multi-stage configurations is crucial. These differences not only impact the gearbox's performance and suitability for particular tasks but also influence design considerations and integration into mechanical systems. 

Efficiency and Performance

  • Single-Stage Gearboxes typically offer high efficiency and performance for applications where a significant reduction ratio is needed in a compact space, but the extreme precision of multi-stage gearboxes is not required. They are ideal for tasks needing robust performance with minimal backlash.
  • Multi-Stage Gearboxes excel in scenarios requiring ultra-high reduction ratios and precision. Their design allows for staggered torque amplification, making them suitable for applications where control and accuracy are paramount over a wide range of speeds.

Torque Output and Reduction Capabilities

  • Single-Stage Cycloidal Gearboxes provide a balance between size and torque output, making them suitable for applications with limited space but requiring high torque.
  • Multi-Stage Cycloidal Gearboxes, through their additional stages, achieve higher torque outputs and greater reduction ratios. This makes them indispensable in applications where slow, powerful movements are necessary.

Physical Size and Application Suitability

  • While both types maintain a compact design, multi-stage gearboxes may be slightly larger due to the additional stages. However, they remain more compact than other gearbox types, offering similar reduction ratios.
  • Single-Stage Gearboxes are often utilized in applications where space is a critical constraint, and the required reduction can be achieved in a single step.
  • Multi-Stage Gearboxes find their place in precision-driven applications, where the highest possible reduction ratio in the smallest possible footprint is necessary, such as in robotics and aerospace.


Choosing Between Single-Stage Cycloidal Gearboxes and Multi-Stage Cycloidal Gearboxes

The decision between using a single-stage or multi-stage cycloidal gearbox largely depends on the specific requirements of the application, including the needed reduction ratio, torque, precision, and available space. Single-stage gearboxes are typically selected for their simplicity and efficiency in applications where space is at a premium, but the demands for ultra-high reduction ratios are not present. Conversely, multi-stage gearboxes are the go-to for applications where precision and high reduction ratios are critical, even at the cost of a slightly larger size.

The selection of a cycloidal gearbox—whether single-stage, multi-stage or a specialized option like Sumitomo's offerings—should always be guided by the application's specific needs. Understanding these distinctions and applications ensures the optimal choice of gearbox, balancing performance, size, and precision to meet the demands of any engineering challenge.

About Sumitomo Cycloidal Gearboxes

Sumitomo Cycloidal Gearboxes, called Fine Cyclo, are known for their reliability and engineering excellence. They combine the benefits of multi-stage and single-stage cycloidal gears. The Fine Cyclo® product series is the ultimate gearbox for high-precision applications with zero backlash. These cycloidal gearboxes are available in both single and double stages and boast a compact design that can be easily integrated into your application. They have an exceptional lifespan and are designed to handle highly dynamic tasks, thanks to their high torsion and low moments of inertia.