Large and small coils


The hollow space can be obtained with large coils (Fig. 77, over-center coiling), or with small coils (Fig. 78, under-center coiling). With small coils, the diameter of the sliver coil (dB ) is less than the radius of the can (rC ). With large coils, the sliver-coil diameter is greater than the can radius. Large coils are generally used in small to medium-sized cans and small coils generally in large cans. The diameter relations should be approximately

\frac {d_C}{d_B} = 1,45   or   \frac {d_C}{d_B} = 2,5

Large coils are better with small to medium-sized can diameters because lower plate speeds can be used for the same circumferential speed (reduction of force, noise, and wear). Moreover, the can capacity is 5-10% higher.

With large cans, however, it is more advantageous if the plate is kept as small as possible, since then less mass has to be rotated.

A speciality is the coiling into rectangular cans as they were developped for optimal space usage.

Fig. 77 – Laying down of sliver in large coils (over-center coiling)

Fig. 78 – Laying down in small coils (under-center coiling)