8.2. Мachine «petra» f. Biancalani For obtaining effects of “worked surface”

Fig. 8.4. Machine «PETRA» (f. “Biancalani”)

Machine «PETRA» originated at the beginning of the 1990s in order to respond to the increasing market demand for "new hands" and "new surface effects" in a wide range of fabrics. The primary objective was to obtain a worked surface that was different from those already obtainable using traditional work processes. In fact, the peculiarity of the PETRA* work process is that of smoothing the fiber, cleaning them of their natural down, leaving a fiber density that can be compared with that of an enzyme-type treatment: an extremely low and dense pile, a fresh and sustained hand. The smoothing bars utilize a very efficient and resistant abrasive material, and their action produces an effect of regular micro-cleaning over the entire surface without attacking the quality of the fiber. Treatments on PETRA* provide for the use of water which, by interposing itself between the fiber and the smoothing unit, delicately cleans the surface of the fabric. This work process also has the objective of preparing the surface of the fabric for the subsequent processes, such as stone-washing, enzyme treatment, and so forth. This process differs from wet systems at present on the market for its homogeneity of effect, absence of selvage center, absence of peeling and, in particular, for the permanence of the effect before and after the dyeing.

Advantages of the machine are

- the action of PETRA* acts delicately on the surface of the fibers, leaving their resistance properties intact; The bars work in water, and their oscillating action in contact with the water and the fabric constitutes the premise for continuous self-cleaning;

- the oscillating action of the abrasive bars produces a smoothing and a typical velvet hand without attacking the qualities of the fibers and without the aid of chemical products or other additives. PETRA* constitutes an original and less costly mechanical alternative to the use of enzymes, both in micro-fibrillation prior to dyeing and also during decolouration after dyeing;

- the incidence of the abrasive bars is absolutely unique for applications on denim, cotton, cellulosic fabrics and linen, of which it brings out the qualities of freshness and the best of the construction features;

- particularly indicated for treatments on denim, in which a decoloration applied previously to that in confection (pre-stone washing) reduces the successive garment treatment to a minimum, guaranteeing a greater resistance of the fabric and drastically reducing lower qualities;

- on dyed fabrics with a relief pattern, it is possible to obtain a three-dimensional effect by means of an abrasive action that is more incident on the parts in relief, which produces an absolutely original decoloration;

- the particular features of fixing industrial diamond dust on the bars confers a long life to the surface which is much greater than that of any other machine to be found on the market, practically no maintenance operations, and very limited costs of re-application, without the need for replacing the bars.

Fig. 8.5. Мachine «PETRA» (f. “Biancalani”)

SMOOTHING MODULE. It consists of six bars with an abrasive surface which is obtained by means of a special electrolytic process that makes it possible to apply a coating of synthetic diamond dust very close to the structure of the bars. This solution guarantees a long duration of the surface and less maintenance, and makes it possible to obtain a decolorisation similar to the one produced by using pumice (stone-washed) - without, however, releasing pollutant dust and sand.

OSCILLATION. The bars move with a high-frequency oscillating movement which produces an action and a counter-action at the same time. From this originates the micro-fibrillation, techno-polishing and decolourisation that do not damage the resistance of the fibers in any way at all.

CONTROL OF TENSIONS. The in-let fabric is stretched out by means of a combined braking, widening and centering system. The tensioning necessary for correctly carrying out the smoothing operation is guaranteed, in modular manner, by a pneumatic dancing roller.

Table 8.2. Technical characteristics of Мachine «PETRA»

Treatment	continuous smoothing of open-width fabric
Maximum work height	180 cm
Entry of the fabric	folding inlet or roller with braking device
Exit of the fabric	in a roll
Treatment speed	2-25 m/min
Tensioning of the fabric	10-160 kg
Number of smoothing bars	6
Oscillating speed of the bars	700 cycles/min
Capacity of the impregnation tanks	250 L
Maximum installed electrical power	26 kW
Average temporary electrical consumption	18 Kw
Maximum temporary consumption of water	250 L/min
Average continuous consumption of water	30-100 L/min
Maximum temporary consumption of compressed air.	250 N/min
Water inlet pressure	1-4 bar
Compressed air inlet pressure	6-10 bar
Maximum width	3860 mm
Maximum length	6600 mm
Maximum height	3110 mm
Weight	8000 Kg

WATER. In addition to exercising a lubricating action during the phase of contact between bars and fabric, thus contributing to the delicacy of action, water makes possible the self-cleaning of the bars during the working phase, as well as the cooling of the same.

RECIRCULATION. During the treatments that permit it, it is possible to activate a water re-circulating system in order to economize on water consumption. The water from the line is introduced only in the last vat in order to guarantee a perfect cleaning of the out-going fabric. From the last vat the water overflow in the first vat, where is re-circulated so as to be sent to the sprayers of the smoothing bars.

MACHINE OPERATIONS AND CONTROL “PETRA” is controlled completely by means of a PLC and is interfaced with a simple and immediate control display. The programming of the speed and tensioning of the fabric makes possible a maximum personalizing of the treatments and their perfect standardization and reproducibility in time. The use of an inverter guarantees an optimal exploitation of the various driven motor. An on-line help system also makes possible a constant check of the machine's running conditions and the immediate detection of the intervention area. The use of an inverter guarantees an optimal exploitation of the various driven motor. An on-line help system also makes possible a constant check of the machine's running conditions and the immediate detection of the intervention area.