Page 119 - Industrial Cutting of Textile Materials

106 Industrial Cutting of Textile Materials

8.3.1 The round knife

The cutting device is a circular knife with a blade sharpened along one side. The knife
rotates and cuts the fabric only in the downward direction. The diameter of the knife
can vary from 80 to 200 mm. The larger the knife diameter, the larger, heavier, and
more powerful is the machine and is therefore less manoeuvrable. The most widely
used machines are those with 100 and 110 mm knives. Blades of different shapes are
used for cutting different materials. Round blades are used to cut light fabrics, but
polygonal blades with 4, 6, 8, and 10 sides are used to cut thicker and harder materi-
als (see Fig. 8.7). The knives may have one or two rotation speeds. Because of large
15
overcut , rotary knives cannot be used to process detailed shapes and sharp corners.

8.3.2 The knife sharpener
The machine has a built-in blade-sharpening system that uses replaceable emery
stones. 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.

8.3.3 The base plate and its rollers
The lowest possible base plate profile is necessary to ensure the stability of the ma-
chine. The base plate facilitates the manoeuvrability of the machine and minimizes the
risk of deforming the material plies during the work process. Independently moving
rollers are fixed under the base plate to ensure easy movement of the machine.

8.3.4 The cable
An electrical cable supplies the motor with electricity. During the cutting process, it must be
secured away from the surface of the cutting table to avoid the possibility of electric shock.

8.3.5 Safety devices
The machine has a front safety shield to protect the operator's hands from the knife
blade. It may also be equipped with an autostop trigger that switches off the power

(A) (B) (C)
Fig. 8.7 The shapes of a round knife, smooth (A), 4 bows (B), and 10 bows (C).

15 The distance between the point of entry of the cutting edge into the material in the direction of travel and
the last point of contact between the edge of the blade and the material.