Since the second half of the 1990s, CANopen has been one of the most important fieldbuses in mechanical engineering, medical technology and many other applications, from smaller devices such as vending machines to large-scale systems such as elevators or ship automation. It has been implemented into many PLCs and into even more embedded- or PC-based controllers.

EtherCAT was introduced in 2003 as an “Ethernet fieldbus” and is now the most successful Industrial Ethernet implementation - with more than 7000 members of the user organization and almost 80 million nodes in the field. EtherCAT uses proven ideas from the fieldbus world - such as the line topology and support of known protocol elements and data structures, for example CoE (CANopen over EtherCAT) - and supplements this with the possibilities of Ethernet such as very fast data throughput, extremely low latencies and optimized transmission media.

Thanks to the comparable communication concepts and data structures of CoE, EtherCAT is an ideal replacement for CANopen - the changeover allows considerably more data to be transferred securely with many more participants in a much shorter time - while the system concept itself can be retained: This means that the same network topology can be used and the EtherCAT controller can also be set up like a CANopen master on various platforms: From small embedded controllers for manageable systems to industrial PCs for power-hungry applications such as measuring systems or complex multi-axis robots.

A pure “data sheet comparison” of CANopen with EtherCAT can be very extensive, as there are many different aspects to compare – and have different significance for any system using CAN or EtherCAT, especially as both networks are used in manifold applications that differ significantly – from simple, small networks e.g. in vending machines to large-scale networks with thousands of devices in complex machinery like ships or fully integrated floor automation.

Speedy networks are mostly seen as beneficial for fast machinery with e.g. fast drives or robots. However, a fast communication network also offers significant benefits for machinery that seems to be slow at first sight. Faster communication might be the basis for accelerating the machine itself, but it can also be used to significantly increase the precision of machinery – thus leading to higher quality processing.

How the fast data-rates and especially the extremely short cycle-time of EtherCAT can help to achieve a significant leap in precision and thus product quality can be visualized in the following example:  Cutting of continuously fed material. This is a typical process in many applications – cutting something to accurate length; whether stiff or flexible materials. Depending on the cutting mechanism and the cutting-duration, several axes need to be synchronized closely.

So as a basic concept - when cutting continuously fed material, the reaction time of the cutting process determines the cutting accuracy.

For example, a jitter/inaccuracy of only 5ms when cutting at a conveyor speed of 2m/s means deviations of 10mm in the cutting process. > If, for example, wooden strips with a length of 1m are produced, the customer will not accept goods with lengths fluctuating by up to 1cm and therefore 1% length difference, either visually or technically.

With a classic field bus such as CAN / CANopen, the transmission of a message with 8 data bytes at 250kBit/s takes just under 500µs in the optimum case (no bit stuffing, highest prioritization, bus free). If the bus is busy or the message is not transmitted with the highest priority, the transmission time is multiplied - in a well-designed system, an average transmission time of 5 to 10 ms can be assumed for important messages - which in the example means that the quality of the result does not meet the requirements. In many systems, transmission times of less than 20ms cannot be achieved and unavoidable cycle time peaks lead to rejects.

EtherCAT offers a reliable cycle due to the specific transmission structure etc. and enables extremely fast systems due to the high transmission speed and simple software structures - with transmission times in the µ-second range.

With a cycle time of 250µs, the accuracy of the cutting process can be significantly increased - assuming a jitter (including software) of 500µs, an accuracy of 1mm can be achieved.

So even with – at first sight – quite simple machinery, the high-speed, high-accuracy control loops possible with EtherCAT make a differenFuce – not just in “raw materials output” but also in terms of accurate and high-quality products.

Of course, there are many more examples, where the fast communication, short cycle times – and in some cases the EtherCAT feature “Distributed Clock” for synchronous operation are key for realization of machinery:

Semiconductor manufacturing -> Lithography: Exposure times must be extremely precise when exposing silicon wafers. Even the smallest deviations can lead to errors in the integrated circuits.
Same is true for etching processes of the wafers: The duration of etching processes must be controlled exactly to achieve the desired depth and shape of the structures.

In classic factory automation, robot-controlled production is only one example: The synchronized movement of multiple robots requires highly precise time measurement – and if we thing about welding robots we add the welding processes itself: The welding time must be precisely matched to the material properties to ensure a stable and secure connection.

There are also many examples in medical technology where timing is key – such as in tumor irradiation: The irradiation time must be accurate to within a few milliseconds to spare healthy tissue and effectively combat the tumor.

To learn more about the advantages for special machine manufacturers when switching to EtherCAT, have a look at the whitepaper below which has been developed by acontis technologies together with our partner Soluware – and watch out for upcoming blogs here at acontis.com!