SUESSEN has been involved in OpenEnd Spinning almost from the very beginning. During a long and successful collaboration with Schlafhorst, SUESSEN designed and made all SpinBoxes SE7, SE 8, SE 9 and SE 10 ever used in Schlafhorst Autocoro machines, a grand total of over 2.7 Mio SpinBoxes. This makes SUESSEN the most successful manufacturer of high speed OE SpinBoxes by far.

Fig-1: Rieter R 40 Spinning Machine with SC-R boxes

SUESSEN continued to develop and improve its SpinBox, even after the collaboration with SCHLAFHORST ended. The results were the Compact SpinBoxes SC 1 and SC 2,which have been used successfully in the modernization of existing SE 8/9 machines. In every mill trial, this SpinBox outperformed its competitor.

After RIETER and SUESSEN' joined hands; the SpinBox SC was further refined and improved, finally resulting in the SC-R. This SpinBox is used in RIETER's innovative Open-End rotor spinning machine R 40. While the author could say a lot about the advantages of the R 40 over its

increase in speed will stretch the fibres, so they will arrive at the rotor not balled up, but nicely elongated. This is most important to achieve good yarn strength. In previous box designs, the fibre channel had to be divided, for reasons I do not have the space to go into. This created air turbulence at the point of division. The turbulence precisely counteracted the speed gradient, by balling up the fibres.

For the SC-F, the undivided fibre channel has been further optimized using FE methods to calculate the air speeds in the channel. The BYPASS has been mentioned before. In Fig. 4, the principle can be explained easily: On conventional spinboxes, all the air, which moves through the fibre channel, is sucked in through the trash chute. The airflow/air speed in the fibre channel should be high, so the fibres detach easily from the opening roller at the point of detachment. Also, the gradient stretching the fibres should be large, again, this requires high air flow.

However, as the name implies, the trash, seed coats etc., is extracted at the chute. The centrifugal force is act-ing on the compact trash particles, forcing them out. However, the air entering through the trash chute is trying to suck them back in. Hence there are two requirements, which seemingly are contradictory:

· high airflow
· high trash extraction

SUESSEN solved this by developing the BYPASS. This is simply an adjustable second opening for the air. When the BYPASS is opened, less air will flow through the trash chute, hence the trash removal is effective. With the BYPASS closed, less trash will be extracted, but also less loss of good fibres.

Normally, we only recommend the settings open, semi-closed, closed. So, for the first time, the amount of trash being extracted can be adjusted by the mill, without affecting other parameters.
The Fixed Fibre Beard Support is important for uniform combing of the fibre beard. In conventional design, feed table and fibre beard support are one unit. The feed table is spring loaded, and moves up/down, to accommodate variations in sliver weight, etc. ln conventional designs, these motions are per force followed by the fibre beard support, hence the point of combing is never fixed in space. Variations in the combing process, and consequently in the yarn are there. With the Fixed Fibre Beard Support of the SC-R, this cannot happen, the combing process is uniform. Historically, OE spinboxes were designed with cotton in mind. Man-made fibres played a lesser role, at most a few spinning components were adapted.
SUESSEN has been the first (and to date the only one) to realize that man-made fibres differ in many aspects from cotton, and not only the spinning components, but the air flow in the box must be optimized for man-made fibres.

· Man-made fibre contain no trash, hence trash extraction is not a big issue.
· Man-made fibres are more flexible than cotton, hence they do not easily detach at the point of

detachment. The dreaded "merry-go-round" fibres are the consequence.
In Fig. 5, the two major adaptations may be seen.
The air volume Q1 at the point of detachment must be large, to facilitate detachment of the fibres. Convention-ally, all this is sucked through the exit of the fibre channel (Q1=Q3).This cross-section, however, should be very small, to deposit the fibres accurately on the wall of the rotor. Again, SUESSEN was able to solve this contradiction by adding the SpeedPass. This is simply a second opening on the fibre channel, to suck more air through it Q4 is added.
The fibres, of course, cannot follow the sharp turn, as they are much, much more massive than air, and are deposited on the rotor wall, as before.
Comparing Fig. 4 with Fig. 5, you see that the wall of the opening roller housing is diverging away from the opening roller in Fig. 5. The result is a cross-section resembling the wing of an air plane (air foil). As is known, this shape causes a difference in pressure between bottom and top part of the wing: An air plane hangs in the air, as the popular saying goes. In our case, also a pressure gradient is created, sucking the fibres out of the teeth of the opening roller, and thus facilitating the detachment.

When SUESSEN designed the Compact SpinBox family with undivided fibre channel, we paid attention to smaller details, also. By way of example, look at Fig. 6.

With the SC-R, the gear driving the feed shaft always remains engaged into the worm shaft. With the competition, it disengages every time, one opens the box. As the worm shaft keeps on turning, there is a chance to damage the plastic gear, when closing the box of the competition. While this might be a small point, why do it wrong, if it can be done correctly without adding cost?

An important issue in rotor spinning is the quality of the piecer. SpinBox and piecer must work "hand in glove'. Let us compare the methods employed by the R 40, vs. its competitor, Fig.7. The competition pieces up, while the rotor accelerates. They measure the speed of the rotor, and estimate the acceleration curve. However, due to tolerances in any measurement, the actual curve of acceleration will be different.

Let us say, they want to piece up starting at speed"s1".They calculate time "a" for the piecing to begin. However, due to tolerances, the actual rotor speed could be "s2" or "s3". Let us further assume that due to mechanical tolerances in the robot, instead of time "a", the robot only starts at time "a+".

Then the rotor speed could even be "s4", instead of the desired "s1 ". By comparison, the R 40 pieces up at constant rotor speed: The rotor acce-lerates to a preset (high!) speed. Then the

rotor is held at this speed, while piecing takes place. After piecing is finished, the rotor accelerates to its final speed. It is clear that this way, small tolerances do not affect the piecing process at all. It is also clear that the piecings will be better and much more uniform, if done at a constant speed. As it is easier to piece up at constant speed, it is obvious that the robot

of the R 40 needs fewer second trials than the competition. This can have dramatic effects on the efficiency of the machine. This method also allows to piece up at higher rotor speeds. The higher centrifugal forces acting on the piecing as it is pulled out of the rotor groove act as a "built-in strength tester": A weak piecing will fail now, not during subsequent processing.

Summary
The SpinBox SC-R incorporates all the experience, SUESSEN has gained over many years, as the world's largest and most innovative manufacturer of OE.

Courtesy: Spinnovation No:19, October 2003