Separating sheets
Separation of flat workpieces from the stack
Flat workpieces stacked in magazines or sheet feeders, such as sheets of paper, cardboard, plastic sheets, foils, metal sheets, and similar materials, are often difficult to separate from one another in an automated process.
They are unstable, adhesive, sometimes moist, statically charged, ridged and simply stubborn.
Separating these automatically and processing them individually is often an insurmountable task for the designer.
Here we show a process-reliable solution for separating stacked flat parts!
Pre-separation through precisely positioned lateral introduction of blown air
Compressed air is dosed and blown laterally into the stack with one or more blowing nozzles.Due to the air flow, the workpieces on top are fanned out separately and float on top of each other without touching.
In order to achieve this effect, it is important that the airflow has the correct distance from the stack and the correct flow rate.If the air nozzle is too close to the stack and the airflow is too directed, a rapid laminar flow develops between the workpieces, which holds the workpieces together.
Therefore, when designing, care should be taken to ensure that the distance and the volume flow of the nozzle(s) are adjustable. The correct distance occurs at the boundary between laminar and turbulent flow.
The amount of air and speed, i.e. the energy of the flow, is responsible for the safe separation or pre-separation of the workpieces.The top workpieces should fan out above the stack, but not lift off in an uncontrolled manner.
The precise and repeatable positioning of the blowing nozzles is achieved simply by using our manually operated positioning units, which can also be combined into multi-axis systems and thus enable adjustment in all durections.
Picking off the top workpiece without compressing the air cushion again
After the workpiece floating above has now been separated from the one below, it has to be picked off while floating on the air flow, without the part below sticking to it again due to the compression of the air cushion.
Our suction lifters were developed precisely for this purpose.
The unique functionality of the lifting suction cup (also known as a vacuum lifting cylinder or drag suction cup) enables the workpiece to be picked up or picked from the stack.
The vacuum lifting gripper reverses the direction of the vertical movement at lightning speed before it compresses the air cushion between the workpieces and the materials stick together again.
The workpiece is thus lifted out of the magazine and can then be fed into the machine.
Der Vereinzelungs-Prozess zusammengefasst
1.
Structure in basic position
2.
Pre-separation by blowing in compressed air lateral
3.
Sensitive picking of the floating workpiece with lifting suction device
4.
Workpiece separated and lifted
Process reliability even with large unstable sheets
For larger workpieces, several suction cups can be connected to one vacuum generator and used synchronously.
In order to ensure optimal parallel connection and synchronous operation, the same tube lengths and the shortest possible distance from the vacuum generator to the suction cups should be selected.
When releasing the workpieces by switching off the vacuum, a blow-off or ejector impulse should be used so that the workpiece is safely and quickly separated from all lifting suction cups simultaneously by the air blast.
This principle is often the only way to separate statically charged, moist, adhesive or burred workpieces from one another without scratching.
In most cases, blast air separation in combination with vacuum gripping works more reliably than mechanical peeling.
Due to its unique functionality, the suction lifter enables lifting out of magazines and picking from different or changing stack levels.