CiA 420: CANopen profile for extruder down-stream devices
The CiA 420 CANopen profiles define the communication between master extruder and extruder downstream devices. The CANopen family of profiles consists of interface specification for corrugators, saws, pullers, calibrators, and co-extruders. These downstream devices communicate solely with the main extruder unit, which also controls the CANopen Network Management (NMT master function).
The PDO cross communication between the downstream devices is not standardized. From the application’s point of view, the extruder is the master and the downstream devices are slaves. The messages sent via PDO from the extruder are confirmed by the downstream devices with corresponding PDOs at the application level. The downstream devices are configured via Service Data Objects (SDO) with the application software of the extruder. The entire communication is pre-defined and programmed in the extruder. System integrators just need to plug the devices together.
Since extruder systems may be set-up and changed over by less than highly qualified staff, system integration must be automatic to a large extent. To achieve the desired degree of plug-and-play functionality some choices within CANopen had to be limited. For example, the CiA 420 application profile for extruder downstream devices does not allow PDO linking for Process Data Objects (PDO). Notwithstanding the plug-and-play function, users may configure additional functions. They may, for example, configure heights, pressures, and temperatures. Additionally, machine builders may offer specific functions. They are thus able to distinguish themselves from their competitors, but partly lose the plug-and-play capability between the devices.