The low weight of film, paper or other 2D fractions reduces the potential throughput performance of sensor-based sorting units. NIR scanners only detect the surface of the supplied objects. All objects must lie separately on the belt and overlapping of objects must be prevented for good performance. All manufacturers' NIR separators need a "mono-layer" for optimal performance.
This is less of a problem for applications using 3D material, since transfer of the objects onto the acceleration belt usually ensures sufficient separation.
This separation process is much more demanding with light 2D components. Because these flat objects tend to fly around and cannot be accelerated at the usual high belt speed of 3 m/s.
Yet for efficient discharge of an object it is essential that the objects to be sorted remain in a stable position on the belt from the time of detection by a sensor. The separator cannot positively separate the corresponding object from the material flow if the object classified by the sensor changes its position after detection or is not accelerated at the preset belt speed. The blast of compressed air calculated by the system is therefore delivered in the wrong place or at the wrong time. The target object in both cases will remain in the continuous flow and cannot be separated.
The usual consequence is that the speed of the acceleration belt is significantly reduced, which reduces the tendency for lifting (flying around) on the belt. Although this reduction in belt speed is counterproductive – especially with respect to light 2D objects. Low surface weight in conjunction with reduced belt speed cause the potential throughput per metre of the separator's working width to further decline. Sorting then becomes uneconomical on aggregate due to the large working widths required.
Clearly better performance with 2D material
The STEINERT UniSort Film is optimised for sorting light 2D material and its innovative design ensures a clearly better performance than standard systems. So the UniSort Film has a high-speed acceleration belt enabling belt speeds of 4.5 m/s. This alone enables around 50% higher throughputs – in comparison to standard systems not designed for film.
The UniSort Film from STEINERT has an elaborate ventilation system for effective acceleration of lightweight objects at these extremely high belt speeds and also to keep them stable in the optimal position after leaving the acceleration belt. A targeted air flow is therefore generated over the entire acceleration belt within the machine and this is synchronised with the belt speed. This means both the belt and the air surrounding the objects are travelling at the same speed. This method allows even light films to be reliably accelerated. The UniSort Film additionally has a specially developed sealing air flow that holds the accelerated objects in the ideal position for sorting, even after leaving the acceleration belt. Without this active object control (AOC) 2D objects are inclined to spin or swirl after leaving the acceleration belt.
The air used for stabilisation and acceleration is mostly operated in recirculation mode, which significantly reduces emissions from the UniSort Film's exhaust.
Typical applications for the UniSort Film are the removal of impurities like paper, card and cardboard (PPC) from batches of film prior to washing or the sorting of 2D packaging waste by PE and PP.
- Mechanics specifically designed for sorting light 2D objects
- Around 50% higher throughputs than standard systems with the same working width
- Recirculation mode
- Increase in plastic ratios
- Enables material recycling of films