Page 116 - Industrial Cutting of Textile Materials

Manual cutting equipment in textile cutting operations 103

Fig. 8.3 Straight knife with a smooth blade to cut fabrics.
8.2.1 The straight knife

The main functional part of the machine is a vertically oscillating straight knife with a
sharp blade. In more powerful machines, the knife is longer, and higher spreads can be
cut (80–300 mm). The width of the knives is between 10 and 20 mm and the thickness
from 0.40 to 0.45 mm. The thickness of the knife is directly proportional to its length.
Double-bevel knives with straight-edged blades are normally used to cut textile mate-
rials (see Fig. 8.3).

8.2.2 The knife sharpener
A knife sharpener is an abrasive sandpaper belt that moves along the knife blade to
sharpen it. It is necessary to stop the work process during the sharpening. The fre-
quency of sharpening depends on the material being cut and on the knife blade.

8.2.3 The presser foot

A presser foot is used to ensure compression of the spread directly in front of the knife
and to decrease displacement of fabric plies during cutting. It also prevents any loosen-
ing of the plies during the return movement of the knife (see Chapter 7, Section 7.4.3).
The height of the presser foot is changed according to the height of the spread.

8.2.4 The base plate and its rollers

A base plate with the lowest possible profile is needed to ensure the stability of the
machine. This facilitates its manoeuvrability 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.

8.2.5 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.
8.2.6 Safety devices

A presser foot is used to compress the fabric plies and helps to protect operator's hands
from accidental cuts. A machine may be also equipped with an autostop trigger that
switches the power off when the operator's hand is removed from the lever. During
cutting, the operator must wear special protective gloves (see Fig. 8.4). These are
made from stainless steel chain mail and give a certain level of protection against stab
wounds or cuts that could occur when the blade moves close to the operator's hands.