Rieter

Type and degree of opening

Index

Two stages of opening must be distinguished:

  • opening to flocks: in the blowroom;
  • opening to fibers: in the card and OE spinning machine.

In addition, the technological operation of opening can include:

  • opening out – in which the volume of the flock is increased while the number of fibers remains constant, i.e. the specific density of the material is reduced; or
  • breaking apart – in which two or more flocks are formed from one flock without changing the specific density.

Breaking apart would suffice for cleaning, but opening out is needed for blending and aligning. Both opening out and breaking apart are found in each opening operation – the degree of each is decisive. If, at the infeed to the card, there is a flock which has been mainly broken apart, but relatively little opened out, then staple shortening will quite certainly result. To enable an exact evaluation to be made of the degree of opening, therefore, both a measure of breaking apart, that is the size of the flock, and a measure of density (in g/cm3) would be needed. Since both measures can be obtained only with considerable effort, the specification of the mass in milligrams/flock usually has to suffice. Such information is provided, for example, by a diagram from Rieter (Fig. 13) showing the degree of opening of several machines as a function of the material throughput. Fig. 14 from Trützschler  [10] shows the increasing opening of the material from one blowroom machine to another. The curve in this example shows, amongst other things, that machines M4 to M5 are already superfluous. They not only make the process more expensive, but also stress the raw material in an unnecessary manner. Their use can only be justified if it substantially increases the degree of opening out (specific density) and thereby improves carding. Fig. 15 represents the ideal form of the opening curve as established by Trützschler  [10].

Table 2 shows opening devices;

Table 3 shows opening variants.

Table 2 – Opening devices

Table 3 – Opening variants

Fig. 13 – Dependence of degree of opening upon throughput; A, degree of opening (flock weight, mg); B, material throughput (kg/h)

Fig. 14 – Increase in the degree of opening from machine to machine in a certain blowroom; A, degree of opening, flock weight in g/flock; B, machine passages; V, feed material; M1-M5, machines 1-5.

Fig. 15 – Ideal form of the opening curve (green line) in an older blowroom; A, degree of opening, flock weight in g/flock; B, machine passages; M1-M5, machines 1-5. It is clearly apparent that machines 4, 5 and 6 are superfluous; in modern lines, they should be omitted.