Minimum possible spacer size of 2.5 mm with 70º shore hardness gives better results in terms of imperfection and hairiness, observe K Buvanesh Kumar, R Vasantha Kumar, and Dr G Thilagavathi.
The ability of the spinner to keep the imperfections down and in turn reduce the yarn irregularities is gaining much importance in this era of stringent quality norms. This paper deals with the effect of combination of spinning spacer and shore hardness. When mechanical faults were kept down to a minimum, irregularities in drafting raised mainly from uncontrolled movement of fibres in the drafting zone(1). As the pressure between the aprons in the drafting zone is controlled by spinning spacer, in turn it governs the degree of control exercised on the floating fibres and as such would have influence over the drafting irregularities.
Evenness and total imperfection could be improved by closing down the apron spacing(2). SKF recommends smallest possible spacer for all the counts. It is, however, often necessary to use a wider spacer for a coarser counts. If there are undrafted places in the yarn when it leaves the front rollers, the break draft should be increased. Spacer should be increased only if the draft results remain unsatisfactory after the break draft has been increased.
This article examines the effect of different combinations of spinning spacers and shore hardness on the yarn quality aspects such as tensile properties, hairiness, etc.
A P/C combed roving of 1.25 hank was produced in the usual manner and 30s combed yarn was produced with the following process parameters.
Count: 30s (P/C 58/42, combed)
Total Draft: 25.2
Twist Contraction: 5%
Break Draft: 1.3
Twist Multiplier: 3.4
Spindle Speed: 14,600 rpm
Drafting System: 3/3, SK FPK 225 spring loaded
Roller Settings: 44x60 mm
Cradle Length: 30 mm
Top Arm Loading: 14x10×x14 KGF
Spinning spacer and shore hardness
The distance between the lower edge of the top cradle and bottom apron nose bar determines the distance between the top and bottom aprons. This in turn determines the intensity of pressure applied to the fibres to be under control. This distance, which is introduced by means of special device, is called Spinning Spacer.
Under identical spinning conditions, the spacer will normally be wider for synthetic aprons than for the leather aprons. This is because with a synthetic apron the fibres will offer greater resistance to forward movement than with a leather apron using the same apron spacer. With widened apron spacing, a progressive deterioration in regularity and strength of yarn was noticed, but the effect was more noticeable only with higher break drafts(3).
The formula has been derived to compute the spacer number to have optimum yarn quality(4). The formula was made up to be effected inversely by two induces called spacer factor and divider. The formula is given below:
Spacer number for Ring frames = (8.233 / (Spacer factor x Divider x vNe)) + 2.03
Spacer factor = (Micronaire value) / (Maturity coeff x 50% Span length (mm))
Divider = (Roving hank x Break draft on Ring frame) + (0.96 / vRoving frame)
The very purpose of introduction of apron drafting is to have an adequate short fibre control during drafting process. These short fibres are to be carried with full control along the surface speed of the second roller as close as possible to the nip and passed forward. Until the fibre is gripped at the front nip, it is expected to be under the full control of the apron during its forward movement. Thus a positive apron control is governed by shore hardness. Any deviation of the apron control from the optimum values will lead to a distorted drafting process, whereby revolving in proper selection of shore hardness, is also detrimental to yarn quality.
Results and discussion
The results obtained in the present study on various properties of ring spun yarn on the basis of different combinations of spinning spacers and shore hardness are shown in Table 1 & Table 2.
|Neps / Km
Properties of ring spun yarn with different spacers and shore hardness combinations:
Effect of spinning spacers and shore hardness on actual count:
As observed from the Figure 1, for both the shore hardness values, increase in the spacer size leads to a small variation in the actual count. However, the minimum variation is found at the combination of spacer 2.5 mm and 85° shore hardness. The count CV% decreases and reaches to the minimum value for 3.0 mm spacer, 70° shore hardness.
Effect of spinning spacers and shore hardness on strength:
The spacer opening seems to have a more impact on yarn strength. From the Figure 2, it is observed that the yarn strength decreases to the minimum value 98.8 with the spacer and shore hardness combination of 3.5 mm and 70°. Therefore, 2.5 mm spacer and 85° shore hardness gives the correct combination to get the better strength as compared to the various combinations. But the minimum strength CV% is observed at 2.5 mm spacer and 70° shore hardness.
Effect of spinning spacers and shore hardness on CSP:
From the Figure 3 it is clearly seen that the CSP value falls down; when the spacer value increases. There is no significant difference in terms of CSP values found between 70° and 85°shore hardness values. However, the highest CSP is found with 2.5 mm spacer and 85° shore hardness.
Effect of spinning spacers and shore hardness on U%:
As spacer value increases, U% gets increased for both the shore hardness. Referring to the Figure 4, 3.0 mm spacer with shore hardness 700° shows the minimum U% of 11.71%.
Effect of spinning spacers and shore hardness on hairiness:
The hairiness value decreases as the spinning spacer value increases. But there is a small rise in the hairiness value at the combination of 85° shore hardness and 3.5 mm spacer. From the Figure 5, minimum hairiness is found at 85° shore hardness and 3.0 mm spacer.
Effect of spinning spacers and shore hardness on total imperfections:
It is seen from Figure 6, that the total imperfections get increased more rapidly for the higher spacer sizes. It is better to use the spacer and shore hardness combination of 2.5 mm and 85°.
· In general it is found that increasing the spacer size decreases the yarn quality parameters. Instead of increasing the spacer size, break draft can be slightly increased.
· From the tests carried out on the combed count of 30s P/C, it is found that, the spacers with 70° & 85° shore hardness are found to have more impact on the yarn quality parameters.
· It is concluded that 2.5 mm spacer with shore hardness of both 85° & 70° are performing relatively well at the same rate. In particular, 2.5 mm spacer with 70° shore hardness gives more advantageous results, as compared to that of 2.5 mm spacer & 85° shore hardness.
· It is found that minimum spinning spacer with minimum shore hardness will give the relatively intended quality yarn.
The authors thank the Management, Principal and Head of the Department of textile technology, PSG College of Technology for providing the facilities to carry out the research and the encouragement extended during the course of the research work. The authors are grateful to the Management of Nisha Kishan Spinning Mills Pvt Ltd, Theni, for permitting to carry out the trails.
1. Balasubramanian N: A study of irregularities added in apron drafting, TRJ, Vol 39, 1969.
2. Bannot B N and Balasubramaniam N: Roving Twist and Apron Spacing upon Yarn Quality and Ring frame End Breakages, JTA, Vol 35, No 4, 1975.
3. Caveny and Foster: JTI, Vol 46, 1955.
4. Shanmugasundaram S: Optimum Spacers For Ring Frames, ITJ, July 1985.
The authors are with the Department of Textile Technology PSG College of Technology,Coimbatore. E-mail: email@example.com