Articles Archive > "EtherCat at DESMA..."

"EtherCat at DESMA..."

Our currently used control technology is the PLC from Bachmann, M1, distributed IOs from Beckhoff and converters / servo drives from LTi-Drives. Generally we use “conventional“ bus systems such as CANopen, Profibus or DeviceNet, partly also together, for communication with the field level in our systems. With these system types the system-typical transmission rate are perfectly sufficient.

Why Ethernet?

Jörn Vonau, Manager Control Engineering at KLÖCKNER DESMA Schuhmaschinen GmbH

March 11, 2010 - Why we investigated alternative communication systems, preferably Ethernet, is justified by

  • simpler wiring
  • more favourably in the procurement
  • higher transmission rates.

 

Combining the suppliers we encountered the EtherCat system.

Simpler wiring by EtherCat...

Standard network cable, no wiring of the buses with additional terminating resistors and different plug versions.

...more favourably in the procurement

By use of far common chip technologies regarding Ethernet the suppliers are obviously able to manufacture the bus modules more favourably. Furthermore no additional bus modules for the PLC are required, connections for Ethernet are usually available. 

...higher transmission rate

Click on the image to go to the web site of KLÖCKNER DESMA Schuhmaschinen GmbH.

With an application, that is a new one for us, two controls separated from each other are to combine in one control system. One of these controls operates as a servo converter monitoring an injection-moulding process by its PLC program. The necessary signal exchange to the machine PLC is made by a “conventional“ field bus system.

 

Our ambition is now to merge the PLC program of the servo converter with the machine PLC. In this connection it was crucial to maintain the accuracy of the injection-moulding process by short cycle times.

 

However, the challenge is not the positioning because the servo converter performs this task by its own. In fact it is crucial reversing the rates and torque limitations at specified points during the injection-moulding process without stoppage and this as accurately as possible at the specified points.

 

A further benefit providing the complete program on one PLC is that a superordinate visualisation gets more simply the process data.

Summary

Basically EtherCat is really a technology DESMA can rely on in the future. However, our experiences have shown that a complete change to this technology makes still no sense.

 

All our suppliers currently in use have still smaller problems in the technical conversion of the protocol although it acts in fact as an open standard.

 

Without knowing the other open Ethernet based bus systems, I am of the opinion that a standard caused by a supplier needs a certain time until all systems whether PLC or distributed modules from all manufacturers will “cleanly” communicate among each others.

 

Basically I am committed for new technologies and will test new technologies together with our suppliers, however, I do not need to be the first one jumping on new technologies using them in series production. (12th March 2010)

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