Hi,
you need to be a bit wary of Ethercat. The Ethercat specification and properties are public documents and manufacturers and
users alike are encouraged to adopt it. There are in effect no license fees, it is built into the cost of the half dozen or so
Ethercat slave ICs. You buy the IC....and make a new Ethercat gizmo with it and you're golden.
Various manufacturers have implemented Ethercat in slightly different ways.....and while that is not supposed to happen; it does.
Yaskawa have been in the business of Ethercat servos for years, and they along with Beckhoff are the accepted industry standard
types for servos and IO modules respectively.
You need to select suppliers of Ethercat slaves with care, some may not operate as you hoped.
There is an organisation, I forget its name, but as a commercial service it offers to test out any Ethercat device for compliance to the
published standard. The cost of doing so is not cheap, but not prohibitive either, maybe 10k. As a consequence all the good manufacturers
of Ethercat slave devices have had their devices certified by this organisation and can market their devices as 'compliant'. You should look for that
compliance.
As a side note ProfiBus and closely related ProfiNet which are broadly speaking similar to Ethercat but will prohibit you from selling any device
without being strictly compliant......and guess who does that compliance testing....they do. Their preferred method of getting the fees is to have you pull
your trousers down and bend over while they extract the funds with cruel instruments! The cost of ProfiBus and ProfiNet products tends to be
much higher than Ethercat.
I use Delta servos, Taiwanese brand made in China, good quality, performance, backup and tuning software at a reasonable price.
Their Ethercat model servo drives are compliant with the standard.
I've seen secondhand Beckhoff IO modules on Ebay at very reasonable costs....so to my way of thinking there really is no need to buy cheaper
or lesser brands when you can have the real thing.
Craig