Reflections on the Spinning of Two-Ply Yarns with EliTwist QCompactSet

Reflections on the Spinning of Two-Ply Yarns with EliTwist QCompactSet

Dr. Norbert Brunk, Technical Director Ring Spinning, SUESSEN

Half a year after the start of series production of our EliTwistQCompactSet,the customers> '>  interest in this new variant of the EliTeQSpinning Method is overwhelming.Some mills already produce these special yarns for weaving and knitting, which exceed all their expectations.Most of our clients approach this new method with a good deal of reflection.

Only in a few cases in short staple spinning wrong expectations have been the source of initial problems. ?.

1. Draft and yarn count range

For the EliTwistQMethod, two separate rovings are fed to each spinning position of a drafting system, which aredrafted and compacted separately. Thus, the doubling effect only occurs

when both components are united in the twisting triangle. This means that both components must be considered as a single yarn of the same count, as regards their possibility of spinning.

Prior to deciding for EliTwistQ it is therefore necessary to evaluate most carefully the spinning limit of the raw material available, particularly if very fine two-ply yarns of about Ne 80/2 andmore are to be spun withEliTwistQ.

Naturally, the SUESSEN HP-A 310/320 TopWeighting Arm permits maximum total drafts of 70-80 without any problem. This statement is based,however, on the prerequisite - as for any other top weighting arm - that p the draft gearing of the basic machine is designed for such drafts and p that the number of fibres in the cross-section of the roving is sufficient for an optimum drafting

operation.So it is not realistic, technologically speaking, to use a specific roving, which up to now has been spun into Ne 50 with a total draft of 40, with the intention to spin two-ply EliTwistQ Ne 100/2 with a total draft of 80. The EliTwistQMethod is subject to the same physical laws and Technological rules concerning raw material, roving count and optimum draft, as the spinning of each of the two yarn components into single yarns.The economic advantages of the EliTwistQMethod always become evident, if conventional two-ply yarn is to be replaced by EliTwistQTwo-Ply Yarn. And in this case there is no discussion with regard to the drafts applicable and so on.It is more difficult, if a single yarn, for example Ne 20/1, is to be replaced by EliTwistQTwo-Ply Yarn Ne 40/2. Here the quality improvements of EliTwistQ must be so advantageous to the Customer, that it is worthwhile to increase speed frame capacity, to feed double roving bobbins and to use better raw material. Since no production increase is achieved at the ring spinning frame in this case.If EliTwistQTwo-Ply Yarn substitutes for conventional two-ply yarn, significant quality improvement and - in addition - economic advantages in the spinning mill take effect.If single yarn is replaced by EliTwistQTwo-Ply Yarn, the price increase achievable owing to improved quality and saving in subsequent processing steps must be directly set against the additional expenditure in the Spinning mill.

2. Yarn Twist

EliTwistQTwo-Ply Yarn can in principle be spun with very low twist owing to the p very small twisting triangle

p leg length of the triangle shorter than half the fibre length p missing spinning triangles in both yarn legs.

A twist multiplier of ae = 3.3 and less is possible in the short-staple range, if raw material and roving quality permit it. This is one of the essential advantages over SIRO.

The minimum twist multipliers attainable with EliTwistQ correspond approximately

to the values that would be possible for spinning one of the two components as single yarn from the same roving.

3. Principle of twist impartation

The EliTwistQMethod is based on the so-called principle of spin-twisting. The sense of rotation in both yarn legs (components) is the same as in the resulting two-ply yarn. Former technical literature includes a multitude of corresponding articles, theoretical research and experiments. It is taken for granted that both legs of a two-ply yarn have about 80% of the number of

twists per metre, which the spindle imparts to the two-ply yarn (see Fig. 2).

Observers of the very short twisting triangle therefore often mean that there is almost no twist in both legs.

This is definitely not the case. A very important positive aspect is even added to EliTwistQ, i.e. the length of both yarn legs is substantially shorter than half the fibre length. From a purely theoretical point of view, the yarn components should not break even if they were not twisted at all.

Furthermore, the two compacted fibre strands ensure that twist is spreading up to the nip point of the delivery roller pair. It is quite obvious that such a combination must result in a very reliable yarn building process, which is realized with much less interruption owing to the additional doubling effect than in a conventional single yarn.

4. Spindle speed

Compared with spinning single compact yarns, there is no limitation.

EliTwistQ permits the same spindle and traveller speeds as single yarn from the same raw material and of the same final count.

Example:

EliTeQYarn Ne 50 is spun at 18,500 rpm. EliTwistQTwo-PlyYarn Ne 100/2 also achieves a spindle speed of 18,500 rpm. Since EliTwistQTwo-Ply Yarns have an extremely low hairiness, it is recommendable to be most careful with regard to running-in of rings and centring of the spinning elements.

5. Advantages over traditionaltwo-ply yarn and SiroSPUN yarn

5.1 Strength

No other spinning or twisting method is able to reach the strength parameters obtained with EliTwistQ owing to the optimized utilization of fibre substance.Tenacity of an EliTwistQTwo-Ply

Yarn is approx. 3 - 4% better than SIRO and about ?5% better than twoply yarn of conventional ring-spun yarn (for worsted yarn it tends to be even better).

5.2 Elongation

Compared with SIRO, elongation is the same or up to ?5% higher, identical spinning conditions (ring diameter, spindle speed) taken for granted.Compared with conventional two-ply

yarn, EliTwistQTwo-Ply Yarn achieves by ?5 to 30% higher values.

5.3 Yarn twist

The twist multipliers possible with EliTwistQ are very low and can still be lower than for Conventional two-ply yarn. EliTwistQ has significant advantages over SIRO, because the running

properties are considerably better. For example, in the short-staple range SiroSPUN yarns cannot be spun below ae = 4.0, whereas our customers with EliTwistQ are spinning successfullywith twist multipliers down to ae =3.3.

For the long-staple sector improvements are even more significant due to the longer fibre length.

5.4 Yarn irregularity

 Uster-CV irregularity of conventional two-ply yarn and SiroSPUN yarn is almost the same. In some cases, SiroSPUN yarn does not quite obtain the parameters of conventional twoply yarn, what is due to the large twisting triangle.In direct comparison, EliTwistQ achieves the best values, because two compacted fibre strands>  spun without spinning triangles are combined after a very short distance. Drafting interruptions in this critical area are therefore excluded.

5.5 Imperfections

As regards imperfections, an EliTwistQ Two-Ply Yarn has approximately the level of a conventional two-ply yarn,whereas SiroSPUN yarn is often slightly worse.

5.6 Surface / Structure

Spin-twisted yarns of the EliTwistQ and SIRO type have a structure, which resembles more to a single yarn than to a conventional two-ply yarn.With a tension feeler, the two components cannot be completely untwisted and separated, what is possible with a conventional two-ply yarn. The pronounced compactness and round cross-section of spin-twisted yarns are remarkable, as their diameter is between 8 and ?2% smaller than of conventional two-ply yarns. EliTwistQ is

in the upper range and seems to be still smoother than SiroSPUN in direct

comparison.

5.7 Snarling tendency

Spin-twisted yarns are more lively than conventional two-ply yarns, and EliTwistQ owing to the additional influence of compacting has the highest snarling tendency. This disadvantage

can be eliminated, however, in most cases, as this yarn can be spun

with a lower twist multiplier.

5.8 Hairiness

Uster hairiness of EliTwistQ is lower by about ?5 to 30% compared with SIRO and lower by about 35 to 50% compared with conventional two-ply yarn.The Zweigle S3 value of EliTwistQ is up

to 50% better than for SIRO. The improvements of both spin-twisted yarns over conventional two-ply yarn are more than obvious.The hairiness values achievable with EliTwistQ can be lower than those of singed conventional two-ply yarns.

5.9 Resistance against abrasion and pilling

What has been said with regard to strength, also applies to the resistance of EliTwistQTwo-Ply Yarns. Test results show that also concerning resistance to abrasion and pilling there is no better spin-twisting process available than EliTwistQ.

6. Running properties in subsequent processing/Efficiency/Ends-down etc.

Sufficient experience in this respect has not yet been acquired, which would allow general statements.Yarnstructure and textile-physical characteristics of EliTwistQ make further improvements probable compared with EliTeQYarns and conventional two-ply yarn from compact yarn.

7. Fibre loss of EliTwistQ compared with SIRO

Fibre loss at the suction tubes is lower by the factor ?0 to ?2 for EliTwistQ in comparison with conventional spintwisted yarns like SiroSPUN or DUOSPUN!!! This is decisive for cleanliness

in the spinning room and processing expensive raw material.

8. What happens if one yarn leg breaks?

If as a result of roving interruption one yarn leg breaks, the twist set for the whole thread, for example Ne 80/2, is running into the existing leg. But as one yarn leg only has half the count of

the whole thread, the twist is much too low now. Due to its insufficient strength, the yarn - as a rule - will soon break.

Example:

EliTwistQYarn Ne 80/2 (= total count Ne 40) with ae = 3.63, i.e.905 T/m.If one yarn leg breaks, the 905 T/m are imparted to the remaining leg. This results in a twist multiplier of ae =2.57!!

If still some metres of this yarn were wound, this would be easily visible by the formation of rings on the cop due to the yarn count divided in two. The personnel should be instructed to take

special care of this phenomenon in case of an end-break.Furthermore, yarn clearers of the latest

design (Uster, Loepfe) are generally in a position to detect such defects at the automatic winder and to clear them.

If one yarn leg breaks as a result of a thin, insufficiently opened fibre bunch or the like, the broken component will immediately and automatically piece up due to the very small twisting

triangle and the two fibre strands approaching each other in a V-shaped constellation. This is realized completely without any auxiliary.The well-known spin-twisting process DUOSPUN requires some complicated device at the suction tube for this purpose.

9. Ends-down rate in the spinning mill

Observations in the laboratory and in some selected spinning mills confirm extraordinarily steady running properties. In any case they are at the level of standard compact yarns,

which have a 50% lower ends-down rate than classical ring-spun yarn, as is generally known.

10.Winding

Restrictions with regard to winding are not known up to now. ??. Splicing EliTwistQ yarn structure resembles much more to a single yarn than to a classical two-ply yarn. Therefore, its

splicing properties correspond to those of single yarn. On principle, the splice of a plied yarn can be seen more easily in a fabric. It may therefore be advantageous to spin EliTwistQ on large-size cops to reduce the number of splices to a minimum.