It is the automation of:
The first step to process tobacco leaves is its preparation. At the preparation area, the product is unpacked and dropped on conveyors where the operators manually remove undesired materials. To assure the flow constancy of the product, which is essential for the whole processing, it is necessary the addition of dynamic weighbelts. These weighbelts issue the feedback reference for the inverters that control the speed of the preparation area conveyor thus keeping the flow of tobacco.
The conditioning step is necessary for the perfect threshing and separation of lamina and stem. The conditioning happens inside the conditioning cylinder. Temperature and humidity are controlled inside the cylinder to create an environment where the leaves open themselves. The precise control of the conditioning parameters results in less production losses and dust generation. Automation at this part of the process means the control of the fan speed and the opening of water and team valves.
This segment of the production line is responsible for the separation of lamina and stem. A good measure of efficiency is the size of the output particles. The bigger the particles, the best is the processing quality. Quality at this part of the processing is quite dependent on the operators skill and experience. Automation helps to achieve better performance by allowing precise control of motors speeds, flaps opening and adjustment of threshers and separators. Operation data can be recorded in data banks formatted as recipes. This recipes are used to reproduce operation adjustments when processing similar classes of tobacco.
After the separation, the lamina must be dried and conditioned. This is accomplished in the lamina dryer. The automation system controls drying and cooling temperature inside the drying compartments as well as the moisture applied to the product along the conditioning compartment. The equipment is set to operate at a steady state prior to the product arrival. Proper adjustments are commanded after the product is first detected at the dryer entrance. Feed back controls are applied when the flow of product becomes stable. In the event of a line stop, a correspondent sequence of control is applied to the equipment. A moisture measuring system installed at the dryer exit and temperature sensors along the equipment feed the plc with the measurements necessary for the dryer control. The presses blockage determine the dryer stop.
After processed, the tobacco is packed in bales or cartons. This is made by pressing the product into the packing enclosures in presses composed of two ore three pressing units. The average net weight is about 200 kg for each box. The automation system controls the precise weight measuring, the pressing sequence, the filling distributors, the boxes positioning and conveyors command. The presses units operate in turns. While one unit is pressing the product in a box, the other unit is filling another box.
The system allows the operator to stop the automation sequence and manually command the equipment whenever required. In case the pressing operation is stopped, a command is issued to stop the dryer.
Conveyor and turntables transport the boxes from the pressing area to the stores. Optical sensors detect the presence of the boxes and command the conveyors to run whenever there is a box to be transported. Motors are turned off when the conveyors are empty for energy saving. Longer conveyors can be used as temporary storage.
After the box is opened, the tobacco is sliced and conveyed to the conditioning cylinder. The automation process consists of controlling the fan speed and the opening of steam and water valves. The goal is to keep the product temperature and moisture constant. A sensor at the cylinder entrance guarantees the operation starts and stops without parameters fluctuations.
Installed before the casing application cylinder, the weighbelt is responsible for the maintenance of the product flow and casing dosage.
Casing is applied to the product according to its flow rate. A PID algorithm controls the pump speed in order to keep dosage at the desired level.
Lamina and stem silos control
Controlling the silos means to automatically select, load and unload them. This is achieved with the addition of level sensors to detect silo emptiness and completion. Distributing conveyors guarantee the uniform loading along the silos. Unloading speed is adjustable according to production requirements.
Flow control weighbelts are meant to keep tobacco flowing smoothly. The lamina and stem dryers performance depends on the product’s flow constancy. The expected result is a homogeneously dried tobacco.
After cut, the product must be dried. The automation system controls the opening of the steam valves and the fans speeds to keep temperature and moisture of the product constant at the cylinder output.
After dried, stem is added to the lamina in a proportion particular for each blending. The master weighbelt measures the lamina flow and issues the reference for the slave weighbelt which in turn adds stem according to the desired dosage.
The flavor application happens inside the flavor and cooling cylinder just after the lamina and stem are blended. A dynamic weighbelt measures the product flow and issues the reference which regulates the flavor pump speed thus dosing this product application.
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