12 stations
KN 1500 clamping force
Theoretical injection volume cm3 30000
Column clearance mm. 560 x 560

TWELVE STATIONS
12 stations plant suitable for the moulding of big sized items by recycled PVC material coming from electric wires, thus polluted by copper residual.

Thanks to the long dated experience in the production of rotary multi-station machines, Presma could select the construction technology as consequence of a marriage between the peculiarity of the final product and the needs connected to the particular raw material used.
In principle the plant consists of an extrusion unit with two counter-rotating screws, diameter 130 mm each, to load the material in the storage head of the "transfer" injection unit.
Due to the particular raw material and to the very peculiar final product, a lot of care had been taken in the study of the extrusion and injection phases, even adopting technical solutions that may be considered risky, right away.
In fact, once the material had been loaded in the accumulator (storage head), the screws stop turning as long as the injection is done. People may think that such long stop of the material, inside the extruder, may cause the burning of the PVC. On the contrary, taking advantage from the peculiarity of the used material, Presma's technicians found a right value of the process temperature thus profiting of the stop to improve the material melting and avoid material alterations.
Moreover, immediately after the end of the injection, the two screws start turning and loading the melted material in the storage head.
The recycled PVC is normally polluted by humidity that is kept under control by an out gassing system and used as blowing agent. The result is that the material flow may fill better the mould cavity, but it causes a counter pressure, thus trying to flow back.
To avoid such trouble the injection puncher is kept against the mould for a certain time, to help the sprue hardening, thus acting as material stopper.
Due to the heavy weight, 30 Kg about, of the pieces to mould and in order to grant a convenient output, the machine should inject large quantity of PVC.
Presma got the choice to make the big injection channels and keep the working pressure at low level, within 500 bar, thus avoiding troubles due the presence of copper wires wastes when working with small channels and high pressure.
Thanks to the solution with big injection channels we may even avoid too long injection time, thus increasing too much the stop at each station.
The clamping power of each station is 150 ton and the expected output of the plant is of 30 pieces per hour, i.e. one cycle every two minutes. Consequently each piece has 20 minutes for cooling and stabilization, as the de-moulding is made in the station 11, after 10 complete cycles.
The piece ejection is made by a manipulator that enters in the mould, cut the sprue, collect the piece, remove it and deposit on a belt conveyor.