Rieter

Need for such assemblies

Index

The so-called combing rate was used previously in order to indicate the opening effect of the card. This was the ratio of the  main cylinder’s rotation speed (rpm) to the infeed speed (inches/min.). This number can no longer be used under modern production conditions. The opening effect can now be represented only by the number of points per fiber, i.e. average of total fibers fed in per unit of time over the number of points available in the same time. At the licker-in there may be, for example, 0.3 points per fiber (three fibers per point) and at the main cylinder perhaps 10 - 15 points per fiber.

If a given quality of yarn is required, a corresponding degree of opening at the card is needed. However, an increase in production at the card such as we have experienced in recent years means quite simply that more fibers must be passed through the machine.

In order to obtain the same carding effect (i.e. the same number of points per fiber), the number of points per unit of time must also be increased. This can be achieved by:

  • more points per unit area (finer clothing);
  • higher roller and cylinder speeds;
  • more carding surface or carding positions;
  • finer opening of the fibers before feeding to the cylinder.

Little can now be done to increase the number of points, since the mass of fiber also has to be accommodated between the clothing: coarse fibers and a high throughput demand coarser  clothing; fine fibers and a lower throughput permit the use of finer clothing.

Much has already been achieved by increasing speeds, but further increases will prove steadily more difficult, as an example will demonstrate. If, for example, the production of a card is increased from 25 kg/h to 60 kg/h with the same number of points per fiber, the main cylinder speed must be raised from 300 rpm to 750 rpm (according to P. Artzt). This cannot be achieved from either the design or the technological standpoint. One effect, among many, would be severe deterioration of the fibers.

There remain only the third and fourth approach – insertion of additional carding surface or additional carding positions and/or installing more  lickers-in. Here also, there are two possibilities:

  • increase in the number of lickers-in;
  • fitting of additional carding plates.

Both have been put into practice.