In motor control applications, hollow-shaft and solid-shaft rotary encoders are essential components of closed-loop feedback systems.
By continuously monitoring the motor’s speed, direction, and angular position, these encoders provide real-time data to the controller. This information enables precise adjustments to the motor’s operation, ensuring optimal performance in tasks such as robotics, CNC machining, and industrial automation.
But here are two questions: What are the key differences between hollow shaft and solid shaft rotary encoders, and how do you choose between the two? In this blog, we will give you the answers, so let’s get started.
What are hollow shaft encoders and solid shaft encoders?
A hollow shaft encoder (also called a through shaft encoder) is a rotary encoder designed with a central hollow bore. This allows the encoder to be mounted directly to a motor or machine shaft without the need for couplings or other mechanical components. The hollow bore is usually matched to the diameter of the target shaft, allowing for direct mounting.
A solid shaft encoder (or standard shaft encoder) is a rotary encoder with a conventional solid shaft extending from the housing. The shaft must be mechanically coupled to the motor or machine shaft using a flexible coupling, gears, or belt drive to ensure alignment and minimize backlash.
As one of the leading incremental rotary encoder suppliers in China, Lorentzzi is able to produce solid shaft incremental rotary encoders and hollow shaft encoders with excellent quality and very competitive prices.
Hollow Shaft Vs. Solid Shaft Rotary Encoders: Key Differences
The main differences between solid shaft encoders and hollow shaft encoders are reflected in structural design, installation method, application scenarios and performance characteristics.
The following is a specific comparison:
| Characteristic | Hollow shaft encoder | Solid shaft encoder |
|---|---|---|
|
Shaft type |
The center is a hollow hole with no protruding shaft |
With solid shaft, external coupling required |
|
Mechanical complexity |
Simple structure, no additional coupling required |
Complex structure, requiring couplings or transmission components |
|
Installation Steps |
Directly put on the target shaft and fixed by clamping ring |
Need to be aligned and connected with the target shaft through a coupling |
|
Alignment requirements |
Automatic centering reduces the risk of installation errors |
Precise alignment is required, otherwise it may cause vibration or error. |
|
Maintenance convenience |
Easy disassembly without disconnecting the coupling |
The coupling needs to be disassembled for maintenance, which is a cumbersome process. |
|
Vibration resistance |
Small mechanical clearance and strong vibration resistance |
Depending on the coupling, vibrations may be transmitted to the encoder |
|
Accuracy and Response |
Direct measurement, reducing errors in intermediate links, high accuracy |
The coupling may introduce mechanical clearance, affecting dynamic response |
|
Load Capacity |
Suitable for light to medium load scenarios (such as servo motors) |
Suitable for high torque, heavy load industrial environments (such as cranes) |
|
Typical industries |
Robots, CNC machine tools, medical equipment |
Heavy machinery, automobile manufacturing, conveyor systems |
|
Applicable environment |
Compact equipment for space-constrained applications requiring quick installation |
High vibration, high torque, complex industrial environment |
|
Cost considerations |
Save coupling cost, lower cost |
High coupling and higher installation cost |
|
Advantages |
– Suitable for high torque and heavy load
– High versatility and shaft diameter compatibility
– Higher durability |
– Easy installation, saving time
– Compact structure, suitable for small spaces
– Reduce mechanical error sources |
|
Disadvantages |
– Complex installation, requires precise centering
– High cost |
– Limited load capacity
– Strict requirements on shaft diameter matching |
How to choose between solid shaft and hollow shaft?
Although the comparison above provides a clear distinction between the two products, the final selection should account for the following critical factors:
- Installation convinience: Hollow shaft rotary encoders are designed for plug-and-play installation. Their hollow bore and integrated clamping system enable direct mounting onto motor shafts without couplings, reducing assembly time and alignment complexity. Conversely, solid shaft encoders demand precise coupling alignment with the motor shaft, increasing both installation effort and risk of mechanical errors. This simplicity is a key reason hollow shaft encoders are increasingly preferred in automation and robotics.
- Vibration consideration: Hollow shaft encoders are less susceptible to vibration-induced errors in low to medium vibration environments due to their direct shaft mounting, which minimizes mechanical backlash. However, solid shaft encoders paired with a flexible coupling can better absorb high-frequency vibrations in heavy machinery, making them suitable for industrial environments such as stamping machines or crushers.
- Space: Solid shaft encoders require a coupling to mount, which takes up a lot of space. For space-critical applications, such as collaborative robots or medical devices, hollow shaft encoders offer a space-saving solution by allowing direct mounting of the shaft without the need for auxiliary components.
- Cost: Since solid shaft encoders need to be used with a coupling, solid shaft encoders are usually slightly more expensive than hollow shaft encoders.
Final Recommendation
Choose Hollow Shaft Encoders if:
- You prioritize space-saving, fast installation, and precision in controlled environments.
- Example: Collaborative robots, 3D printers, or lab equipment.
Choose Solid Shaft Encoders if:
- You need ruggedness, high torque tolerance, or compatibility with existing couplings.
- Example: Mining equipment, automotive assembly lines, or wind turbines.
Conclusion
All in all, hollow shaft encoders offer more advantages compared to the solid shaft ones, which is why more and more people choose hollow ones rather than solid shaft types.
If you have further inquiries, please don’t hesitate to contact our professional technical support team at shonxu@lorentzzi.com. The Lorentzzi® team is ready to assist you anytime, anywhere.
