Page 155 - Industrial Cutting of Textile Materials

142 Industrial Cutting of Textile Materials

gantries and one or more parallel-driven cutting heads on the same gantry (‘KoriumJeť
11
by Tecno Systems ).
The material is placed on a grid kind of surface (honeycombs) above the water
tank that captures the water under the cut material. Sheet or rolled materials can be
processed. To increase productivity processing sheet kind of materials, movable shut-
tle tables can be used (see Fig. 10.5). In processing rolled materials, cutting table is
equipped with a roll stand spreading system.
Water-jet treatment is also used for denim fabric and garment finishing. In the pro-
cess called water-jet fading, strong jets of water remove colour gradually until the fab-
ric gets the desired shade of blue. These nonchemical procedures cause little damage
to the fabric.

Advantages of the water-jet cutting: Water-jet cutting does not generate levels of heat that
would harm textiles. It is possible to process very narrow and sharp corners and difficult
contours. There is no deformation as the cutting forces are very small. Clamping devices
are rarely needed. As only one cutting device is used that does not need to be sharpened,
changed, or cooled during the cutting process, only a short cutting program needs to be cre-
ated, and no time loss occurs in setting the machinery and tools for subsequent orders. The
jet is so thin that it does not even wet the material. The water consumption is low; it produces
a low wear and tear of the components. The maintenance costs of the water-jet system are
low comparing with other kind of cutting systems.
Disadvantages of water-jet cutting: Although there is no danger of fusing as in the laser or
plasma cutting methods, there is a tendency for cut edges to mesh together, making it diffi-
cult to separate the plies.

9.5 Automated ultrasonic cutting systems

The use of ultrasound for processing hard and brittle materials has been known since
the early 1950s. The development of new multiaxis CNC ultrasonic cutting systems
began in 2001. Ultrasonic cutting systems are designed to cut thermoplastic materials:
composites, flooring, textiles, thermoplastic films, and rubber. They are also used in
food production. These systems can be operated as hand-held units or incorporated
into automated machinery.

9.5.1 Characteristics of the ultrasonic cutting process
High-frequency sound energy is generated inside the horn and focused at the cutting
tool fixed in the horn (see Fig. 9.28). The cutting tool vibrates or oscillates rapidly.
This generates a lot of heat in most synthetic materials and melts the fibres that are
parted by the cutting tool. The blade (chisel), which vibrates 20,000 times per second,
does not cut by force or speed, but by vibration. The vibration of the cutting tool
must be resisted by a hard surface; therefore, a special metal or plastic top must be
fixed on the work surface of a cutting system. The cutting tool can be shaped to suit
different processes. A sharp tool will give a good cutting action with reduced sealing,
but a rounded tip will give a better seal. The shaping and choice of tool tips for any