EtherNet/IP vs EtherCAT – Machine Builders Doing Motion Control

One key decision machine builders must make is what industrial protocol to use. Two protocols we often see are EtherNet/IP™ vs EtherCAT. Let’s compare these two protocols for machine builders in synchronized motion control.

 

What’s the Difference Between EtherCAT vs. EtherNet/IP?

EtherNet/IP and EtherCAT are industrial automation protocols. They move input/output data between controllers and endpoints on machines. The key difference is in how they do this.

EtherCAT moves I/O data over physical Ethernet, processing on the fly with nodes and an EtherCAT master. EtherCAT is fast and flexible, especially paired with KEB embedded IPCs.

EtherNet/IP is transported via Ethernet cabling using TCP/IP. This protocol is based on Ethernet standards, making it accessible to IT teams. High-performance servo drives across standard Ethernet networks support EtherNet/IP.

What Is EtherNet/IP? The Basics

EtherNet/IP is ODVA’s execution of Common Industrial Protocol (CIP™) over Ethernet. It’s mainly associated with Rockwell Automation.

EtherNet/IP is an application-layer protocol implemented over TCP/IP. It uses the same hardware as office networks. Each EtherNet/IP device can send and receive messages from any other EtherNet/IP device.

Inexpensive CAT5 network cables can connect EtherNet/IP devices. IT departments and engineers will be familiar with its wiring and general operation. Control and standard network traffic coexist on the same cable.

EtherNet/IP can’t provide real-time performance or within a specified time frame. Jitter can be quite large, along with other network traffic, affecting machine control. This may negatively affect machines that require repeatable performance.

EtherCAT – The Basics

Beckhoff started EtherCAT, and now EtherCAT Technology Group (ETG) manages it. EtherCAT is also transmitted over the Ethernet physical layer with inexpensive CAT5 cabling.

EtherCAT uses a “processing-on-the-fly” approach, in which the EtherCAT master sends a main telegram. Each node reads its own input data and adds output data to this message. The telegram cycles to all connected nodes and returns to the master.

ASIC chips enable this process on EtherCAT slave devices. The result is fast, efficient data transmission. EtherCAT devices can operate synchronously, bringing jitter down to a few microseconds.

EtherCAT also supports high node counts without sacrificing performance. This makes it well-suited for large, complex machines.

EtherCAT and EtherNet/IP in Real Machine Scenarios

High-speed packaging lines

EtherCAT: EtherCAT can process on the fly, which keeps communication cycles short and jitter low. So, devices can act in tight synchrony, which can be critical when stopping a filler diverter within fractions of a millisecond.

EtherNet/IP: EtherNet/IP can be more limited in this context. Rather than fractions of a millisecond, this protocol runs at full millisecond performance and with higher jitter. This can cause delays or inconsistent responses during what should be time-critical tasks.

Servo-driven indexing systems

EtherCAT: The efficient processing brought on by data flow in a single network means every servo gets its updated command and status within the same cycle. So, there is reliable synchronization with minimal latency, making it ideal for tight servo loops in indexing.

EtherNet/IP: EtherNet/IP can sometimes struggle to guarantee deterministic cycles across servo nodes. That’s because it relies on standard Ethernet timing mechanisms, and these can be less predictable under heavy network loads.

Multi-axis synchronized motion

EtherCAT: EtherCAT designs support synchronized motion control with low jitter and repeatable cycle times. So, they support precise multi-axis coordination without the need for additional hardware.

EtherNet/IP: Did not support tight motion control originally. EtherNET/IP required CIP Motion and Sync layers to be developed, and while they help, they don’t often match EtherCAT’s native real-time performance.

Robotics or material handling system

EtherCAT: EtherCAT is suitable for complex robotics due to its deterministic cycle and support for a high number of nodes. OEMs will choose EtherCAT for its low latency and precise synchronization.

EtherNet/IP: Broadly speaking, EtherNet can support plant automation and integrate with PLCs and IT infrastructure. It may also coexist with standard Ethernet traffic and benefit material handling systems that way. Though, motion extensions may still be required for a true robotic sync.

Network Flexibility

EtherNet/IP supports many network topologies. Each device must have an IP address and follow the same subnet as other devices.

EtherCAT does not use IP addresses. The order of network wiring defines each device, and single-panel machines can daisy-chain from device to device. EtherCAT Extenders support star and tree topologies, and dual EtherCAT ports support ring topologies.

Slave nodes have an embedded termination resistor, with no added network termination required. This simplicity gives EtherCAT the network advantage for basic machines.

Performance: Synchronized Motion Control

Scan Time vs. Cycle Time

PLC scan time refers to how fast the controller executes its logic. Network cycle time, meanwhile, determines how often I/O and drive data receive updates. In synchronized motion systems, deterministic network cycle time matters more than PLC scans.

Vanilla EtherNet/IP does not handle synchronized motion control tasks well. Because of this, a new profile called CIP Motion™ was developed.

CIP Motion uses a time-based model to perform motion control tasks. It’s often coupled with CIP Sync™ to ensure real-time performance.

EtherCAT supports synchronized motion control right out of the box. Efficient handling of telegram info and the ASIC enables extremely fast update rates.

EtherCAT is known for its low jitter, allowing higher synchronization between axes. EtherCAT component vendors can provide tested jitter info.

 

Functional Safety (FS)

EtherCAT (FSoE) and EtherNet/IP (CIP Safety) offer networked FS options if your machine needs functional safety. These allow safety I/O, switches, and drives to communicate safety parameters over the bus system.

Both safety protocols are independently certified to a SIL3 level.

Ubiquity of Suppliers

ETG does an incredible job attracting active vendor members. There are currently 500+ vendor member companies offering ETG products.

Part of this success is due to EtherCAT’s high performance. Another part is due to ETG’s free memberships and royalty-free EtherCAT installation.

Having several vendor members gives machine builders more product choices. EtherCAT customers have many options for controls, drives, I/O, encoders, safety, etc.

The rapidly increasing number of EtherCAT products is a huge advantage for machine builders.

Value – Price to Performance Ratio

A simple value equation has performance on top and price on the bottom. By increasing performance, a product manager will increase value.

Similarly, decreasing cost increases value. Value goes up when performance improves and price decreases.

Which Protocol Is Better for Machine Builders?

For motion control applications, EtherCAT is clearly the winner in performance. It’s designed for low jitter and real-time performance without any special hardware.

Machine builders save money by avoiding the cost of managed switches. The wide availability of EtherCAT products also drives down prices, reducing overall costs.

EtherCAT offers a distinct advantage for machine builders based on performance and price. Based on performance and price, EtherCAT offers a distinct advantage for machine builders.

KEB provides EtherCAT controls, IO, Servo Drives, VFDs, HMIs, and Safety products. Contact us for your motion control needs.