The complete homogenization of the dough takes place during the transport towards the die, as a consequence of the pressure exerted by a worm screw. The compression is applied by an extruder comprised of a cylinder with a rotating worm screw inside it. The heat generated during the compression stage is drawn off by a water-based cooling system surrounding the cylinder..
The viscose, homogenized and compact dough passes through a steel mesh filter on the die. This filter traps any impurities that may have escaped the previous sieves, the "clots" that sometimes form in the kneading machine, and regulates the entry speed into the die.
The compressed pasta passes through the “screw”, through the filter and into the die to take its definitive shape.
The die has special characteristics for each individual format to be produced; there are dies for short pasta and for long pasta. For short pasta shapes, the dies are normally circular made from a bronze and aluminium alloy disc. The most common die diameter in recently-built plants is 520 mm. The surface of the openings can be bronze, to create a rough light yellow, surface or coated in teflon to create a bright yellow smooth surface.
The shaping of the short pasta takes place by compressing the pasta into openings of different shapes and sizes.
The dies for “pierced” shapes have a cylindrical core, supported by tiny supports, inside the pasta shaping channel, which allows the pasta to form the desired hollow formation (e.g.: bucatini)
For long pasta the dies are normally rectangular in shape and from 1 to 1.3 metres wide; they are also made from bronze and aluminium alloy. These have openings where the die inserts are fitted to give the dough the characteristic shape. The shaping of long pasta takes place by compressing the dough through the openings made in the inserts.
20 minutes have passed since the semolina was placed in the kneading machine. The pasta-making operations are controlled by specialised personnel using computerised systems that record each stage using dedicated sensors and allow, based on the detected conditions, the management of all parameters (temperature, humidity and speed) to provide an optimum result.
With short pasta, when the pasta leaves the die it is cut by a rotating knife with two or three blades. The rotational speed of the knife is inversely proportional to the length of the pasta. A powerful jet of hot air, simultaneously surrounds the pasta to eliminate the surface humidity and prevent the pieces of pasta from sticking to one another during the subsequent stages.
On long pasta production lines, the product is collected onto long metal rods and draped over them, ready to proceed onto the drying stage.