Rieter

The drive problem

Index

Energy accounts for some 10% of a spinning mill‘s manufacturing costs (at 20 tex), and the ring spinning installation itself for some 2/3 of this. Even if this does not seem a very high percentage, it is a cost factor that should not be underestimated, especially since there is potential for economies in the energy sector if the correct types of drive and power transmission are chosen. For example, in a ring spinning mill with 25 000 spindles and a total of 7 000 operating hours/year, in which an average of 1 million dollars is spent on energy, savings of 10% produce some very interesting figures. This power input is used on the ring spinning machine primarily for:

  • spindles (with travelers) 65-70%
  • drafting systems 25%
  • ring rails 5-10%

However, the technological problem is much more serious than the economic aspect, since differences in yarn tension arise during winding onto the  cop. It would be useful to reduce these differences in tension by means of variable spindle speeds. If the ring rail rises during layered winding, i.e. from a large to a small winding diameter, yarn tension increases substantially, e.g. from 25 to 40 cN, and ends down frequency increases accordingly. According to a study by Zinser, most thread breakages occur when the ring rail rises in the upper (not the highest) zone (Fig. 40). In order to maintain thread tension and ends down at constant levels, spindle speeds should be reduced when the ring rail is raised (control of layering speed).
The problem with winding as a whole is similar, since the balloon is very large (Fig. 41, I1) at the beginning of cop buildup and relatively small at the end (I2). Yarn tension varies accordingly. Adjustments should also be made here via  spindle speed (control of the basic speed). Both speed adjustments were previously made by means of the commutator motor. Nowadays it is mostly only the basic speeds that are changed via variable speed gears, DC motors or frequency-controlled drives.
For this at least a startup step (to prevent startup thread breakages), a base step (for forming the cop base) and a normal step (for winding the cop as a whole) should be available as control options. There is often also a spin-out step for winding the topmost part of the cop, which can be identical to the base step.

Fig. 40 – Ring rail motion, yarn tension and ends down frequency during a ring rail traverse (Zinser) (simplified)

Fig. 41 – Different balloon heights