CAN embedded in industrial automation machines
Source: CAN Newsletter September 2007
CANopen is one of the most important embedded machine control networks. It is used in very different machines. Normally, there is a PLC with NMT master functionality and several motion controllers and I/O modules connected to the central controller. Most of these applications use the pre-defined CAN-IDs for PDOs, Server-SDO, and Heartbeat or Node guarding. Motion control applications often use synchronous PDOs in order to synchronize several axes.
Wood sanding machines
Homag was one of the first users of CANopen as embedded machine network. The market-leading wood processing enterprise uses for example CANopen drives from different manufacturers.
The Bütfering Schleiftechnik in Beckum, Germany, belonging to the Homag group, produces solid wood sanding machines, which use steel contact rollers, rubberized contact rollers and the sanding pad. These allow work-pieces to be processed in one operation cycle of the machine. These wide-belt sanding machines perform calibration, coarse, pre-sanding and fine-sanding operations. The machines are controlled by PLCs providing interfaces for AS-Interface, CANopen and Profibus.
Extruders and downstream machines
Another industry that uses CANopen is the plastic and rubber machine builders. In a cooperation between Euromap and CiA, several profiles for extruder downstream devices have been developed. Some of these machines also use CANopen as embedded control network inside the individual machines. Boston Matthews (Worchester, Unite Kingdom) uses a CANopen network to communicate between the PLC and the extruder downstream devices.
Printing machines
The printing machine industry has adopted CANopen as embedded control network and as open network for up- and downstream devices. Heidelberger printing machines has developed several CANopen interfaces for dryer and other subsystems. The Stitchmaster ST400 is a stitching machine based on a controller, which connects up to 30 units via the CAN network. The central controller broadcasts the position of the virtual shaft every 3 ms to all units. Additional CANopen networks are installed in each unit as well as in the stitching machine. More than 200 of these machines have been sold so far.
Book binding machine
Solema from Pedrengo, Italy specializes in machines for book and brochure production also uses PLCs and other automation devices. The larger machines are based on CANopen transmitting synchronous PDOs in order to transport the magazines simultaneously.
Packaging machines
Packaging machines are highly automated. Few of them require higher speed communication than CANopen can provide. However, in many packaging applications, synchronous operations are necessary. CANopen with the Sync mechanism is well suited for such tasks. Examples include coffee pads packaging machines as well as machines packaging cookies.
Carton gluing machines
Another example is a folding box machine that folds and glues the cartons. Wächter Packautomatik from Bad Wünnenberg in Germany uses a CANopen-connected PLC for its Catojet food packing machines. In many of these machines, the PLC provides also Ethernet or Profibus interfaces to communicate to factory management systems.
Outlook
In many of this kind of machines, CANopen is used as front-end embedded network, while Profibus and increasingly Ethernet provide communication between systems and machines. CANopen drives and I/O modules as well as other automation devices are available from different manufacturers. In particular, the CiA 402 CANopen motion control and drive profile is one of the reasons, why machine builder select CANopen as embedded control system.
