The sawtoothlike wire and the flexible clothing. Flexible lothings (Figure 1) have needles embedded in a base strip, made up of layers of felt or flexible material.

Fig. 1 Flexible clothings

Wires (Figure 2) are made up of a steel thread with sharp-edged teeth. This makes them quite wear-resistant.
When it comes to choosing between wires and flexible clothings, it must first be remarked that there are, in general, clear advantages to be derived from using former. These advantages are, first of all, increased production levels, because wires are rarely saturated and the material is less recycled, and a less frequent need to carry out cleaning and re-sharpening, which consequently leads to a reduction in idle times. Furthermore, the life of wires is many times greater than that of flexible clothings, which means that they also cut costs considerably; finally, precisely because of the short time the fibres themselves remain on the card, wires also cause fewer fibre breaks, thus the semi-processed product has a longer average fibre length.

Fig. 2 Sawtooth wires

However, there can be major obstacles to the use of wires on cylinders other than those of the pre-carding unit, where sawtooth wires are essential in order to effect the first and the most intensive opening operation. One, when materials are particularly heterogeneous, is the presence of foreign bodies in the blends: in this situation, wires are more liable to break, and to sustain serious damage, than flexible clothings, because while the latter spring back quite easily, wires can often become irreparably dented, making it necessary to replace many metres.
Another contraindication for the use of wires can be the presence of very greasy blends.
Excess grease, that has not been absorbed by the fibres, is deposited on clothings. If these are flexible clothings, it becomes mixed with the layer of fibres that are deposited at the base of the clothing needles. Thus, it is periodically removed during cleaning. Wires, on the other hand, which become just as contaminated with grease, gather far fewer fibres and this makes them more difficult to clean. Finally, with wires, the material is not recycled to the same extent, and the carding and blending effect is less pronounced.

Fig. 3 Curved needle

The flexible needles currently used are all curved knee-type needles. This is because, as they flex (Figure 3), the simultaneous rotation of the knee and foot allows the distance between the clothings to be kept constant, guaranteeing even processing and accurate counts.