# Rieter

### Piecing

#### Index

After combing of the fringe protruding from the nippers, the detaching rollers draw some of the combed feedstock out of the sheet. This produces a tuft with a length dependent upon the staple length, but lacking all internal coherence. By means of the piecing operation, the rollers have to lay these newly formed strips of web on top of each other so that first a coherent web and finally an endless sliver is obtained. For this purpose, the single fiber tufts are laid on top of each other in the same way as roofing tiles (Fig. 19).

Consequently, piecing is a distinct source of faults in the operation of the rectilinear comber, but is system-related due to the discontinuous process. The sliver produced in this way has a wave-like structure, i.e. it exhibits periodic thin and thick variations.

$L =PD \times V_{total}$

 L Wave Length PD Piecing Distance Vtotal Total Draft

(source: Uster Tester 5 handbook)

These variations are visible in the mass spectrogram (Fig. 20) as combing cycles in the form of so-called piecing peaks (at about L 30 - 35 cm, due to draft height in the drafting unit). This long-wave, sinusoidal piecing fault is reliably leveled out in the subsequent autoleveler drawframe.

Example: Piecing period is shown at a wave length of 60 cm. With 6-fold doubling and drafting on the RSB drawframe, the periodic fault should be visible at 3.6 meters in the RSB spectrogram – but this is not the case. It has been leveled out. Another thing is the correct table draft (tension between delivery roller after eccentric withdrawal and infeed roller of drafting unit).

Fig. 19 – Combed web structure (section view); PD – Piecing distance or piecing period, FL – Fiber length, AL – Detaching length, FP – Fiber package length> AL + FL

Fig. 20 – Examples: Mass spectrograms after combing and in downstream processes