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Hi

Forewords: I am total beginner in CNC-world so my questions may be a little dumb.

For another project I designed a controller board that has ethernet-connection and stepper motor controllers + several digital I/Os.

For that same project, I am going to build a cnc router (to make parts) and I started wondering if it would
be possible to control cnc-machine from EMC over TCP-connection?

New PCs do not have parallel ports any more and I have had my share of add-on card mess.

I wonder if it would be possible, instead of creating stepper control signals over parallel port, send control over TCP?
In the controller board end it would be very easy to run motors based on the commands received over TCP and likewise easy to read limit switches,
encoders etc. and pass that info back to EMC.

I did search this forum and google but either this is something nobody has done or I was using wrong keywords.

-MJ-

I would say TCPIP is not a good match for EMC because it is nowhere near real-time
Possibly with a dedicated Ethernet card on the host (or MB with two Ethernet interfaces) and UDP you might get passible performance.

I think better choices are RTNET (which uses standard Ethernet hardware) or EtherCAT (which uses standard hardware on the host but special slave hardware) Note, all Ethernet options require a dedicated Ethernet connection, so you still may need add-on cards...

New controls with Ethernet servo drives using CIP Motion and CIP SYNC protocols are coming out (IEEE1588 based technology).
They promise sub-millisecond servo loop update time using regular Ethernet connection and even faster by using switches with QoS
It would be nice to have something similar for EMC2

Is CIP is really real time? the fact that CIP needs IEEE 1588 and timestamp based protocols to skip
over late packets seems to say even its promoters don't trust its real time abilities.

CIP as it was introduced years ago is not a real time, but widely used for I/O control.

CIP SYNC is relatively new variation of CIP and it can deliver timestamped data with sub-microsecond accuracy, I saw and used CIP SYNC enabled devices to get time synced accross the network

CIP MOTION is very new, later this month Rockwell Automation (www.ab.com) will be releasing new version 18 of ControlLogix that will have CIP motion implemented, I beleive drives with etherenet interface are out already.
As far as I understand, control and drive sync'ed their clocks first using CIPSYNC, and timestamped data will be coming over UDP multicast with periodic clock corrections. This technicsally will replace SERCOS interface

While what was said about CIP sync is true, there is one potential problem that I know of. When it comes to rigid tapping or some similar operation all the axis must be coordinated to the spindle position. Even If the spindle position encoder is connected directly to EMC2, and not over the CIP network, I don't know it this will be too limiting. Of course one could always tap slower and it would work, but we need to figure out what maximum delay and jitter can be tolerated. The other problem with CIP sync is that ODVA does not give the standard away for free. It costs $1000 for a copy. On the plus side, CIP sync uses standard ethernet hardware unlike etherCAT which requires a special MAC. Many suppliers are now offering ethernet with IEEE 1588. The best way to implement IEEE 1588 is to use hardware in the phy for the time stamp.