SIZE PRESSES

Description

The aim of the Size Press is to apply a solution of starch, glue or colour to the dry surface of the paper. This operation improves the mechanical and printing atributes of the sheet. Other benefits can be to reduce the tendency to become dirty, to increas strength and to reduce its air permeability.
The impregnation of the sheet can take place on one or both sides of the sheet.
A series of jets with adjustable flow creates a sump between the two pressing rolls, the side collecting tanks maintaiming a uniform concentration of the additive.
The rate of transfer of the web through the nip determines the impregnation of the sheet on one or both sides.
For web impregnation of the sheet on one side only, the size press is equipped with a lubrication system with a jet of nebulized water on the "dry" cylinder.

Specifications

The machine is designed for semi-automatic operation.
The web coming from the pre-dryer section is guided by paper-guide rolls through the size press. Subsequently, while the rolls rotate in synchrony with the machine speed, the operator controls the closing of the of the press nip.
The opening of the nozzles is automatic when the appropriate photoelectric sensors indicate the presence of a full width web in the machine.
The approach of the cylinders is very fast, whilst the definite closure is relatively slow in order to prevent sheet breaks.
The operator sets up the working pressure on the nip and the PLC process runs all the sequences, the hydraulic unit and its pumps in accordance with safety procedures.
The prerator chooses to use of the cleaning doctor in either fixed or oscillating mode.