Through Hole Slip Ring vs Pancake Slip Ring: Main Differences, Applications & How to Choose - Blog

Introduction

In rotating equipment, selecting the right slip ring is crucial for the stable operation of the system. Through-hole slip rings and pancake slip rings are two common types, each suited to different space constraints and operational requirements. This article will explore the differences between them, their typical applications, and offer practical tips for choosing the right one.

What Is a Through-Hole Slip Ring?

A through-hole slip ring, also known as a hollow shaft slip ring, is a cylindrical electromechanical device with a central bore. During operation, cables, shafts, or fluid lines can pass smoothly through this hole. It typically uses a design of ring-shaped brushes and conductive rings, allowing multiple power, signal, or even data channels to transmit simultaneously while maintaining stable performance during continuous rotation.

What Is a Pancake Slip Ring?

A pancake slip ring, also known as a flat slip ring or disc slip ring, is a flat, disc-shaped rotary electrical connection device. It has a low axial height and a large diameter, making it specifically designed for equipment with limited axial space. It typically consists of multiple layers of concentric conductive rings and sliding brushes, enabling multi-channel signal transmission. However, due to structural limitations, its current carrying capacity and number of channels are generally lower than those of through-hole slip rings.

Main Differences Between Through Hole and Pancake Slip Rings

Here's a quick comparison of the main differences between through-hole and pancake slip rings.

Comparison	Through Hole Slip Ring	Pancake Slip Ring
Shape	Cylindrical with a central bore	Flat, disc-shaped
Space Occupancy	Higher axial height, flexible radial space	Low axial height, larger radial footprint
Electrical Connection	Multi-contact brushes on conductive rings	Flat rings on PCB / spring-loaded brushes
Signal Channels	Supports up to 120 circuits (ByTune standard)	Fewer channels, typically 1–18
Speed Range	300–10,000 RPM	60–100 RPM
Current Capacity	High current carrying capacity	Lower current capacity
Installation	Mounted through a shaft	Mounted on a flat surface
Typical Applications	High-speed rotating systems, shaft-integrated equipment	Systems with limited height, flat structure setups (rotating displays, robotic joints, etc.)

How to Choose the Right Slip Ring?

Choosing the right slip ring requires considering the equipment's structure, operating conditions, and electrical requirements. The following key factors can help you make an informed decision:

Need for a Central Bore

If your design requires a central hole for routing shafts or piping, a through-hole slip ring is the most suitable choice. Otherwise, a pancake slip ring can be considered.

Space Occupancy

When vertical installation space is limited (axial height is constrained), such as in camera gimbals, turntables, or compact mechanical devices, a pancake slip ring is recommended. If installation space is sufficient, a through-hole slip ring can also be used.

Current and Channel Requirements

Systems that require high current or multiple channel transmission should prioritize a through-hole slip ring, while pancake slip rings are typically used for low-load applications where signal transmission is the main concern.

Speed Requirements

High-speed continuous rotation systems are better suited for through-hole slip rings, while low-speed or intermittent rotation devices can use pancake slip rings.

FAQ

Q: Can a pancake slip ring operate at very high speeds?

A: Not entirely. Due to its flat structure and limited brush contact area, a pancake slip ring is typically suited for low-speed or intermittent rotation. High-speed continuous operation may affect stability and lifespan.

Q: Are through-hole slip rings more durable?

A: Generally, yes. Through-hole slip rings are designed for industrial environments, with a robust structure that can withstand higher mechanical loads and continuous high-speed rotation, making them generally more durable than pancake slip rings.

Q: Can pancake slip rings be used for data transmission?

A: Yes, but signal quality may degrade at high-speed data transmission. For stable high-speed data transfer, fiber optic slip rings or capsule fiber optic slip rings are recommended.

Q: What is the maximum bore size of a through-hole slip ring?

A: ByTune offers through-hole slip rings with bore sizes ranging from 3 mm to 500 mm, depending on the model and application requirements.

Conclusion

Both through-hole and pancake slip rings can be used to transmit power or signals in rotating systems, but they differ in structure, space occupancy, performance, and installation. If your system requires high current, high-speed rotation, or a central bore for shaft routing, a through-hole slip ring is the better choice. For designs with limited axial space, low-speed operation, or primarily signal transmission, a pancake slip ring is more suitable.

Not Sure Which Slip Ring Is Right for Your Project?

As a professional slip ring manufacturer, ByTune offers high-performance slip rings, including through-hole slip rings and pancake slip rings, as well as customized solutions. Simply tell us your requirements, and we will help you select or design the most suitable model.
Contact us today for a free technical consultation or to request a sample.