Posted to News on 16th Sep 2008, 15:28
CC-Link connects conveyor inverters to PLC network
A CC-Link communications systems links inverters controlling the speed of conveyors in a cigar factory, thereby ensuring quality is never jeopardised.
Cigars have a finite shelf life, so production has to respond to demand, including sudden seasonal fluctuations. The processing plant therefore has to be able to vary its throughput over a wide range, while maintaining high product quality.
The key process in cigar manufacturing involves breaking down bales of compacted tobacco then working it up into expanded tobacco so that the final cigars draw smoothly. The tobacco is then fed as loose material via conveyors into the conditioning cylinder - which is similar to a huge washing machine, wherein water and steam are added to the tobacco to make it pliable.
From here the leaves are transported via a vibrating conveyor belt to loosen them, and then they are sucked up by a vacuum into a section where the tobacco's moisture content and other characteristics are checked. Tobacco that passes this quality check is then transported by a series of conveyors to a bank of holding silos, ready for cigar production.
Four-fold expansion
When the tobacco is needed, it is sent to two expanded filler treatment areas via more conveyors. The expanded filler plant treats the tobacco to achieve the correct texture for production. The tobacco then enters an airlock, where a vacuum is applied to remove moisture from the leaves. It is screw-fed through the airlock and pentane gas is added to make the tobacco leaves expand to four times their normal size, giving a better smoking experience.
After the pentane has been added, the tobacco is packed into boxes of 20kg by a network of conveyors and worm screws and is sent to the next stage of the complex tobacco treatment process.
A CC-Link network connects the 20 conveyor inverters to the PLC network that forms the plant's control system. This high-speed fieldbus network allows the inverters' speeds to be constantly checked and adjusted to match the rest of the process speed on a real-time basis. The CC-Link network also enables the inverters' alarms to be monitored, with resetting of any problems co-ordinated from a central maintenance SCADA system.
