Page 133 - Industrial Cutting of Textile Materials

120 Industrial Cutting of Textile Materials

top (flat and pointed top). The angle of the blade (from 30 to 60 degrees) depends upon
the properties of the material to be cut. The blade angle is smaller the thicker materials
can be cut and vice versa. Different thickness and properties of materials can be cut
by changing the extension of the blade and cutting pressure. Drag knives are good to
cut detailed shapes, sharp corners, small circles, and notches. The cutting has to be
performed on a special, hard material cutting surface that cannot be damaged by the
sharp blade of the knife. Drag knives are used for thru cutting thin materials and in kiss
cutting applications to cut corrugated or very tough textiles, paper and plastic, leather,
rubber, and composites. Kind of more robust blade, called tangential knife, is used to
cut heavier, thicker and harder materials than by the traditional drag knife. By help
of one more servo motor it can also rotate/turn during the work process to follow the
direction of the cut lines in the challenging material (a drag knife is drugged without
any direction control).
Advantages of the tool: The drag knife ensures the highest cutting precision and speed com-
paring to other cutting tools, a cost-effective cutting tool.
Disadvantages of the tool: The drag knife creates certain drag forces that try to displace
material on the cutting surface. As all cutting force is concentrated in one point – in the
top of the angled blade of the knife – a drag knife affects cutting surface more than a
round knife.

9.3.1.2 Round knife

The round (circular, rotary) blade knife during the work process rolls over the ma-
terial (see Fig. 9.6). The round knives vary in diameter and shape of the blade. The
diameter of the knife depends on the properties of the material and the complicity
of the contours to be cut. The small diameter blades (18 and 28 mm) are used to cut
thinner materials, small shapes, and accurate curves. The large-diameter blades (45,
60, and 70 mm) are used to cut thick materials when detailed cutting is not required.
The 28 mm-diameter round blades are most commonly used to cut different kinds of
textiles. The shape of the round blade can be continuous or segmented (see Fig. 9.7).

Cut material

(A) (B)
Fig. 9.6 Round knife: round knife in a cutting process (A) and photo of a round knife (B).