PROCESS

The technological process for the fabrication of metal, polyurethane insulated, composite panels, better known as “ sandwich panels”, by means of a continuous line, can be thus outlined:

Unwinding of the steel coils and surface embossing
The prepainted sheets (see COMPOSANTS) are placed at the beginning of the production line as steel coils which weigh a number of tons.The material is positioned on uncoilers by means of specially equipped loading machine. Immediately after the continuous uncoiling of the steel sheets, an adhesive transparent film of polythene is applied, which serves as protection for the following phases of production, packaging and handling by the user, who will be able to remove it by means of a simple “peeling” operation. The sheets are now protected and able to endure a surface embossing which offers an aesthetic finish suitable to the type of use for which the panels are to be employed (industrial: STUCCO; residential: WOODGRAIN (see COATINGS FINISHING)].

Profiling of the steel sheets
The profiling of the steel sheets, which constitutes the surface of the panels, is carried out by means of two profiling machines (for the lateral edges of the sheets this is done by a two border machine in order to characterise the nose and tail of the panel, and for the microribs, this is done by two full width rolls), which work simultaneously on two levels, external and internal, on the continuous steel sheets coming from the coils, embossed as mentioned above. Each profiling machine is equipped with a driving system which is able to vary and synchronise their own speed, and also the speed of the other sections of the production line. The two profiled sheets are then supported and guided to the following section of the line.

Stamping of the sheets
Before the profiling machine, on the external side of the panels, there is an equipment which carries out the moulding which is used for the so-called cassette raised “Georgian type” panels. This procedure is divided into various phases:

• Entry loop system control
• Electronic power source
• Moulding press
• Dye
• Exit loop system control.

Preheating of steel sheets
In order to allow for the correct activation of the chemical reaction of polyurethane isolating foam and in order to allow for its adhesion to the metallic sheets, before reaching the foaming section, the sheets are preheated by an automatic heating system. The temperature is controlled by law regulated instruments which regulate the thermal power necessary for the stability of the set point value.

Automatic positioning of the reinforcing internal inserts

Distribution of the foaming mixture
After heating the surface of the sheets, a suitable amount of chemical components, stoichiometrically measured, is laid onto the lower sheet. This mixture of chemicals generates a rigid polyurethane isolating foam with insulating cells, and without CFC, by means of a chemical reaction of expansion and polymerization. The perfect mixture of the chemical components is obtained in a high pressure foaming head that receives, separately, every product from its respective measuring pump each controlled by its own electronic capacity meter and calculated by self-regulated software based on the set point values . The most important chemical reagents in the mix (polyol and isocyanate) are kept at the required temperature in order to activate the chemical reaction, which is developed in an exothermic way (by heat generation). The foaming head is assembled on an adjustable structure which allows for oscillation along the whole width of the sheet/panel so as to form an alternative system of distribution of the foam that leaks from the nozzles of the foaming tube.

Formation of panel
The reaction of expansion and polymerization of the foam takes place at the same time as the profiled sheets pass through the double belt conveyor, which is constructed in order to rigidly contrast the pressure which is developed by the expansion of the foam during the filling of the panel (high/low; right, left), which is then formed in the appropriate section of the line. The slabs of the conveyor are maintained at a set temperature by heating ovens, in order to guarantee a correct control of the expansion reaction on the inside of the conveyor.

Labelling panels/marking of the lots
Once out of the conveyor, when the panel has been formed, an ink printer, with non erasable ink, labels the production with numbers which indicate at set intervals: order number, production date, and a progressive number which allows for the identification of the panels produced until sent to their final destination.