Magnetic And Vacuum Stackers

In the early nineties SALICO developed a brand new concept that changed completely the technology of advanced stacking of sheets with sensitive surfaces. The new concept was called the "zero inertia" or "start-stop" stacking.

 

Up to that moment the existing vacuum and magnetic stackers available in the market were transporting the sensitive sheets under moving belts to which they were adhering with either vacuum in the case of non ferrous materials and stainless steel, or with magnetic forces in the case of carbon steel. The problem came at the moment of releasing the magnetic forces or the vacuum, when the cut sheets due to the inertia of the translation motion, described a parabolic motion in the air that normally was stopped with a hit against the back stop or against the upper side of the previous sheet, producing marks on the edges and/or on the surface of the sheets that were not acceptable for many applications.

 

The different constructors of stackers in order to reduce the impacts of the sheets against the back stops or against the previous sheet, made many attempts of reducing the parabolic motion of the sheets by making different sizes of the vacuum chambers or the magnetic elements with more valves and actuators for a more precise and progressive control with sequential shut down of the vacuum or of the magnets, but at the end it was clear that the only way to stack the sensitive materials avoiding any single mark on both the edges or the surfaces of the sheets, was to reduce the line speed and therefore to reduce the inertia of the sheets. Of course this had a very big and negative impact on the productivity of the Cut to Length Lines, that were featuring very high speed eccentric rotary shears (also invented by SALICO) with very slow stackers.

 

The developments from SALICO at those days ran in a different direction to others and instead of reducing the speed of the sheets our target was the opposite: increasing the speed of the sheets by steps permits to separate them and then having sufficient time to fully stop the motion in the internal side of the stacker and just on top of the stacking station. At that moment with the sheet located right on top of the stacking station and not running, the sheet could be stacked properly - inertia free - without any risk of damage.

 

So with this invention the belts in the stacker are continuously accelerating and stopping very precisely and once the speed is zero, the vacuum or the magnetic forces are released and the sheets drop without inertia and in a vertical and controlled way on top of the package.

 

Nowadays SALICO remains as one of the very few, if not the only manufacturer of Cut to Length Lines in the world that is designing and manufacturing its own vacuum and magnetic stackers using this operation principle, while most of our competitors are buying their stackers from external stacker producers, with many of them having adapted with the years the zero inertia concept once invented by SALICO.

Vacuum Stacker

Magnetic Stacker