Page 123 - Industrial Cutting of Textile Materials

110 Industrial Cutting of Textile Materials

The cutting machines operate with either a fixed knife speed (e.g. 14 or 16 m/s) or an
adjustable speed that accommodates a wider range of fabrics (8–18 and up to 30 m/s).

8.5.2 The knife sharpener

The machine has a built-in blade-sharpening system. It is necessary to stop the cutting
process during the sharpening. The frequency of sharpening depends on the material
being cut and on the knife blade.

8.5.3 The work surface

The work surface of the machine (see Fig. 8.11) is smooth and may be equipped with
a special air-blowing system (see Fig. 7.23). This creates an airspace under the cut
fabric, which facilitates its manoeuvrability. The air pressure is adjustable. The surface
may have also a special air filter to remove the dust created during cutting. The height
of the table is adjustable between 820 and 920 mm. The machines are available with
work surfaces of varying sizes. The more powerful machines will usually have larger
tables.

8.5.4 Safety devices

As the cutting is performed at high speed by a very sharp steel band, special attention
must be paid to the safety of the work process. A warning light indicates that the power
is on, so the operator knows that the band knife is running. The machines also have
an automatic safety stop. In case of band-knife breakage, the machine will stop within
2 s. A presser foot that compresses the fabric plies and is fixed in front of the knife also
helps to protect the operator's hands from injury (see Fig. 8.13). During the cutting
process, the operator must wear special protective gloves (see Fig. 8.4).

8.5.5 The disadvantages of working with the band-knife
machine
The limited size of the work surface of the machine and its cutting path (the cut mate-
rial has to be moved against the knife) limits the size of the cut components. Because
the components are moved manually and are generally small, the operator's hands
come very close to the cutting device, creating the danger of injury.

8.6 The fabric-drilling machine

Special drilling machines are used to make drill marks straight through multi-ply
spreads (see Fig. 8.14). Usually, these are made after the components have been cut by
placing the drilling machine onto the component bundle (see Chapter 7, Section 7.3.2).
The drills may be made in fabric spreads of up to 300 mm in height. The weight of the
drilling machines varies between 5 and 13 kg.