Simplified closed-loop servo-pneumatic positioning technology from Festo has revolutionised a large and receptive new market in volumetric filling by cutting wastage and reducing costs. Volumetric filling applications typically demand very precise control for drawing and dispensing fluids without splashing, foaming or unwanted aeration. The key to the success of the Festo solution is the company's innovative SPC200 servo controller.
This device allows exceptionally fine multi-positional control of standard pneumatic actuators.
It offers two benefits in volumetric filling applications: the ability to draw and dispense accurate volumes of material at defined velocities by directly driving the pump mechanism with the actuator; and the option of withdrawing the entire dispensing head and nozzle from the carton or container as the liquid is deposited.
Some filling installations deploy an array of 12 or more dispensing nozzles across a production line.
Each nozzle needs to be adjusted to deliver an exact amount of material.
However, changes in viscosity due to factors such as ambient temperature, original ingredient consistency and mixing procedures can result in variations in weight for a given volume between product batches.
Adjusting heads to compensate takes time and can waste product.
Typically, to guarantee that at least the stated minimum weight of product is dispensed to the container, most systems overfill by a small percentage.
Over time, this is a costly excess, and one which can be minimised by Festo's more accurate and controllable filling process.
The Festo solution uses a pump -style piston assembly which first draws product from a hopper or header tank, switches a valve to redirect the flow path, then dispenses the product through nozzles into containers on a process line.
However, the SPC controller can halt the actuating cylinders at any position along their stoke to eliminate the need for manual compensatory adjustment.
In addition, the SPC unit under PC or PLC control can go one stage further.
It can integrate feedback from an in-line weighing system to make automatic on-the-fly dispensing adjustments.
Each head can be independently driven and controlled to ensure a perfect fill with negligible wastage every time.
Now the target weight is constant with small variations in the volume dispensed automatically compensating for the process variables.
The Festo approach to volumetric filling is truly revolutionary by combining process precision with low cost.
In the past, pneumatic solutions have not been readily considered to deliver the accuracies needed, while servo-electric mechanisms are precise but expensive.
Successful results have been achieved with leading manufacturers on a diverse selection of products including cheesecake, water, cream, pre-mixed wallpaper paste, chicken soup, custard, instant potato and high-value mineral oils.