Techniques of making stretch yarn and fancy yarn without any attachment

Elastane fibre has the property of stretching and so it is used in making stretch yarn. Fabric with stretch yarn provides the wearer comfort, durability, wrinkle resistance and freedom of movement. Therefore, such fabrics are in high demand.

Even in denim and other fabrics for making some styles of trousers, stretch yarn is widely used and 80-85 per cent of the domestic demands for them are with stretch yarn in the weft.

Making core spun cotton stretch yarn

Probable methods of core-spun yarn production are discussed below:

1. Conventional core spinning attachment with ring spinning systems

2. S.R.R.C core wrap spinning method

3. A.R.S. patterned spinning system

4. Core-twin spinning system

5. Composite electrostatic spinning system

6. Rotor spinning system

7. Friction spinning system

8. Air jet spinning system

We started a project of making the stretch yarn on rotor spinning. Initially, we inserted the elastane yarn into the rotor with various methods so that it would spin with cotton and give the stretch yarn. One of the ways in which we got the stretch cotton yarn is given in below Figure 1. In the method shown, we inserted elastane yarn from the back of the rotor and due to centrifugal force inside the rotor, elastane yarn comes in centre of cotton. This gives us core spun open end stretch yarn from the take up rollers.

Fig.1. Making the open end core spun stretch cotton yarn

The above process has many limitations since it requires a lot of modifications for the elastane yarn to enter the rotor. We have checked fabric made with such yarns but there were issues like uneven stretch.

After the trial mentioned above, we spun the elastane yarn with cotton into the ring frame. This is shown below in Figure 2.

Fig. 2. Spinning elastane yarn with cotton without attachment on ring frame

We have found that feeding elastane yarn into the front roller causes different stretch in denim fabric. There are no stretch quality issues after making denim fabric but when the fabric was washed, there was a difference in stretch. Therefore, we were not successful in this trial but were able to successfully invent fancy yarn, discussed later.

After brainstorming to make the stretch yarn without attachment, it was decided to feed the elastane yarn into speed frame during roving process. We have taken finer hank at speed frame and 70 single count (s) denier elastane yarn and have put in the centre of roving into front roll with small holding attachment of elastane yarn. We have not set any draft into the spandex but only given tension draft in speed frame. We have put the speed frame bobbin directly into the ring frame and spun the yarn normally. The production of stretch yarn turned out to be just like the production of normal yarn, without having to change the speed. With this process, we got the following yarn for denim fabric.

Nominal Count :	7 s SPANDEX
Yarn parameters	Tested parameters
Actual count(ne)	6.73
Lea strength	268
Actual csp	1804
Cv% of count	1.51
Cv% of strength	2.19
Uster unevenness
Lycra %	3.1
(Uster-iii,400m/min)
U%	11.35
Thin places/km (-50%)	5
Thick places/km (+50%)	31
Neps/km (+200%)	38
Total imperfection/km	74
Tested after conditioning	No

We made denim fabric with the above yarn and put it through various washes to give the same effect as stretch yarn. The same process can also be used to make stretch slub yarn. This saves money as there is no need to reduce speed or drop production like in a stretch attachment.

Fancy yarn with conventional ring frame

As per Figure 2, we have made core spun yarn by using polyester as a core. It was covered with cotton. We have taken 80 denier polyester yarn for core and fed it into the front roller. We have taken cotton hank of 1.2 Hk from inter machine and fed it into the ring frame. Ring frame feed was adjusted for making 48 single count and finally we got the 27 single count core spun yarn of polyester covered with cotton.

The above trial produced the following yarn:

Nominal Count :	30s P/C ( 80 D Poly+ 48s CO )
Supplier By:	G 5/1 Ring frame
					Average
	TM 3.8
	27'PC	27'PC	27'PC		27'PC
Yarn parameters
Actual count(ne)	27.04	26.32	26.46		26.6
Lea strength	116.43	127.42	127.88		123.9
Actual csp	3148	3354	3384		3295.2
(uster-iii,400m/min)
U%	13.01	13.08	13.55		13.2
Tn -50	5	2	8		5.0
Tk +50	651	636	695		660.7
Nps	757	711	896		788.0
Total	1413	1349	1599		1453.7

We have made the denim fabric of 30s x 27s constructions and discovered linen-like effect after washing. As polyester yarn remains in the core, it will provide the feel of cotton fabric even though it has been used in the weft.

With such yarn process, finer count can be made in courser ring frame while simultaneously decreasing the cost of yarn by 25 to 30 per cent by using low cost mixing.

OE yarn converted into ring yarn

We can convert the OE yarn into ring yarn. After doing a trial, we have made 10 single count OE with less TM of 4 (Normally 5.2) in OE yarn. This OE yarn spool was put at the ring frame creel of ring frame and was fed the low TM OE yarn into front roll of ring frame. We have given TM of 1.2 into Ring frame and made yarn. We have got the yarn which gives ring effect and at every stage, we have checked parameters which are given below.

 

 

Nominal Count : 10S OE		10s Carded Ring yarn
Supplier's Name : In House
TM	4	1.2
Yarn parameters	Tested parameters	Tested parameters
Actual count(ne)	9.96	9.52
Lea strength	194.97	226.48
Actual csp	1942	2156
Cv% of count	1.17	1.00
Cv% of strength	7.52	3.71
Twist per inch
Actual tpi	12.62	15.02
Cv% of tpi	2.24	2.19
Uster uneveness
(Uster-iii,400m/min)
U%	9.71	8.88
Thin places/km (-50%)	0	0
Thick places/km (+50%)	7	5
Neps/km (+280%)	2	10
Total imperfection/km	9	15

We used this yarn in denim fabric and it provides ring effect instead of OE effect. We have made OE slub yarn with higher taper in slub so we got excellent ring slub yarn with the above process.

We thus eliminated ring spinning preparatory i.e. inter process and can make the ring yarn with low-cost OE mixing. This saves 15-20 per cent in making ring yarn over the conventional method.

Courtesy : 
Piyush Chandarana & Bharat Thakar