Impact of long ring spinning frames on yarn cost

Editorial board, Pakistan Textile Journal / Professor Emeritus,
Textile Institute of Pakistan

This article is reproduced from the April 2007 issue of Pakistan Textile Journal.

During the spinning of fibres into yarn cost is incurred at each processing stage. In general, the processes involved are preparation of homogeneous mixing, blowing, carding, doubling and drafting, preparation of roving and spinning. The ring cops produced on ring spinning or compact spinning machines are rewound to produce cone or cheese by using winding machines. The open-end rotor spinning machines produce a marketable package directly from finished drawframe sliver eliminating roving frames and winding machines. However, the processes mentioned above are indispensable in the case of ring and compact spinning. The approximate contribution of each process to the cost of conversion of fibres into yarn is listed below. (1)

The above data shows that ring spinning frame is a significant cost factor in spinning mills. Almost all major textile machinery manufacturers are continuously engaged in research and development of ring spinning machines with the object of reducing spinning process cost. For example Suessen (2) has developed FIOMAX RC, a high speed sliver to yarn ring spinning machine which eliminates the roving process and the cost associated with it. This machine is capable of processing cotton and short staple fibres with a count range of 6 to 60 ne.

Another important development is the manufacture and marketing of Long Ring spinning Frames. The possibilities of reduction of the conversion cost involving the use of long ring spinning frames are discussed below.

1. Area of Ring Shed

For the same number of spindles, the area of the ring shed of a spinning mill comprising of long ring spinning frames is less than that required for short ring spinning frames. Both types of ring sheds are illustrated in FIG-1 and FIG-2 of the ANNEXURE-1.

The saving in the shed area with long frames is calculated on the basis of following assumptions:-

» Total number of spindles = 18,144
» No. of short ring spinning frames 504 spindles each = 36
» No. of Long ring spinning frames 1008 spindles each = 18
» Width of short as well as Long ring spinning frames = 820mm (EJM-128 model ring spinning machines marketed by Shanghai Erfangji Co. Ltd.)-(3)
» Distances of the main alley, central alley in case of short ring frames and side alleys as shown in the sketch at Annexure-1

Width of the sheds = Length of short Ring Frames = 2650 + 251× 70 = 2650+ 17570= 20,220m.m.
Length of shed with short Ring Frames- FIG-1, Annexure 1.

= 3890+ 20220+ 4000+ 3890
= 5 2220 m. m. = 171.33ft.

Area of shed with short Ring Frames = 171.33×159.416
Area of shed with short Ring Frames = 27,312.743 sq ft. ----------- (a)

Length of long Ring Frames = 2650+ 503×70 = 2650+35210 =37860 m. m.
Length of shed with long Ring Frames = 3890+ 37860+ 3890= 45640 m. m.
Length of shed with long Ring Frames = 149.738 sq. ft – FIG-2, Annexure- 1.
Area of shed with Long Ring Frames = 149.738× 159. 416
Area of shed with Long Ring Frames = 23,870. 5546 sq ft. --------- (b)
Saving in shed area with Long Ring Frames = 27,312. 743- 23,870. 556
Saving in shed area with Long Ring Frames = 3442. 187 sq. ft.

Saving in construction cost of Ring shed with Long Ring Frames @ Rs 700/- per square foot = 3442.19× Rs 700 = Rs 2,409,533 – say Rs 2.41 million

2. Electric Power Consumption

The lesser area of the ring shed comprising of long ring frames will result in lower Consumption of electric power required for illumination and air-conditioning as compared to the shed with short ring frames. The heights of the two sheds will be equal. The saving in electric power consumption will be approximately as follows:-

Saving in the area of ring shed with long frames = 3442. 187 sq. ft. Assuming air-conditioning requirements@ 8watts per sq. ft and illumination requirements @3 watts per sq. ft. saving in electric power consumption per day

3. Yield of yarn

In the case of shed with long ring frames, two facing sides of adjacent machines can be allotted to a four sider for attending to piecings of end-breaks and associated work. He can patrol the length of the long ring frames without the necessity of crossing the central alley which would be indispensable in the case of allotment of four sides of adjacent machines, two on one side and two on the other of the shed with short ring frames. FIG-1, Annexure

1. Supposing that the four sider crosses the central alley 6 times per hour while patrolling, the extra distance covered by him is calculated below:

The width of the central ally = 4000 m. m. = 13.12 ft.
Distance covered by four sider per 8 hours = 13.12× 6× 8= 629.76ft.

The four sider working on long ring frames will not spend his time in covering this extra distance during the shift. This will facilitate timely detection, piecing of end-breaks and reduction of pneumafil waste. Supposing pneumafil waste is reduce by 0.2%, the yield of yarn will also improve by the same percentage. The saving in the cost of cotton for producing the same quantity of yarn is calculated below.

Assuming the cost of cotton @ Rs 2500/- per maund and improvement in yield of yarn (20Ne) from 84% to 84.20%.

4. Changes in Production Program

The spinning mills prepare and implement production programs according to the requirements of the market for various counts of yarn. In line with the fluctuations in the market demand, the spinning mills change their respective pattern of production. Assuming that change of count is required from 20 Ne to 30 Ne on 10 short ring frames. Each machine will be stopped for the changes as follows:

Escalation in the conversion cost originating from stoppage of machines for count change on short ring frames has been calculated on the basis of fixed cost of the spinning mill at Rs 13.0 million. Cost per spindle shift works out at Rs 7.961. OPS (ounces per spindle shift 20 Ne have been assumed at 10.

In the case of short as well as long ring frames conversion cost per LB. of 20 Ne yarn = = Rs 12. 738

The escalation in conversion cost per LB. of yarn on account of stoppage of 2 hours and production loss is calculated as follows:

Escalation in conversion cost per LB. of yarn in the case of long ring frames = Rs 13.51 –Rs 12.738 = Rs 0.772.
Redirection in conversion cost escalation = Rs 1.157 – Rs 0.772
Redirection in conversion cost escalation = Rs 0.385 (per LB. of yarn)
Saving in conversion cost in case of long ring frames per count change per day. = 5 × 1890 × Rs 0.385 = Rs 3638.25

5. Machinery Maintenance

The number of head stock and off- end gearing sections in the case of 18 long ring frames will be reduced by 50% as compared to 36 short ring frames for the same number of total spindles i.e., 18144.

Similarly, the number of main motors, suction motors and ring rail lifting motors will be reduced by 50 %.

Consequently, the mechanical and electrical maintenance work will also be reduced by about 50%. Thus, the requirement of personnel for attending to the maintenance work will also be reduced in both cases. The resultant saving in the salaries of the staff is calculated below.

5.1 Mechanical Maintenance

The spinning mill with 36 short ring frames (504 spindles each) generally employs 2fitters, 4 assistant fitters and 15 helper fitters for mechanical maintenance of machines involving cleaning, gauging and overhauling work in addition to 1 foremen and 1 head fitter. In case of 18 long frames (1008 spindles each) services of at least 2 assistant fitters and 6 helper fitters can be dispensed with. Saving in the salaries paid will be approximately as fallows:

Salaries of 2 assistant fitters per day @ Rs 5000/-per month = Rs 333.33
Salaries of 6 helper fitters per day @ Rs 4000/- per month = Rs 800, 00
Total saving per = Rs 1133. 33

5.2 Electrical Maintenance

The spinning mill with short ring frames as mentioned above employs 1 motor fitter, 1 motor winder, 4 electricians and 1 general operator in addition to 1 engineer, 1 foreman and 1 head electrician for electrical maintenance work. In the case of long ring frames services of at least 2 electricians can be dispensed with resulting in the following saving:

Salaries of two electricians per day @ Rs 6000/- per month = Rs 400-
Total daily saving in expenditure on machinery maintenance = Rs 1533.33

6. Summary of Reduction in Conversion cost

Excluding the saving in capital cost for construction of the ring shed, the impact of long ring frames on yarn conversion cost as calculated above is summarized below:

Daily production of the spinning mill under consideration, i.e. 18 long ring frames, 1008 spindles each on the basis of an average count of 20Ne = 34,020 LBS.

Impact of long ring frames on yarn conversion cost and reduction per LB = Rs 0.27

In view of the advantages of long ring frames discussed above almost all major machinery manufacturers are offering these frames as listed below:-

1. EJM 128 (Shanghai Erfangji) = 1008 spindles per machine.
2. G 33 (Rieter ) = 1200 spindles per machine.
3. RX 240 (Toyoda) = 1056 spindles per machine.
4. UAH (Howa) =1024 spindles per machine.
5. Fiomax 1000 ( Sussen) = spindles per machine.
6. Alfa 25 (Savio) = 960 spindles per machine.
7. RST – 1 (Marzoli) = 1296 spindles per machine.
8. RM 351 (Zinser) World’s longest ring spinning machine = 1680 spindles per machine.

Many spinning mills of Pakistan, especially the big groups, are also engaged in replacement of the short with long ring frames as a part of their respective BMR programs.

Acknowledgement

Technical information received from M/s. Bilal Wajid, Azam Naeem, Muhammad Ali Khan, Bilal Javed, Raheel Roshan Ali and Iftikhar Ahmed Soomro is gratefully acknowledged.

References

1. W. klein, “A practical guide to ring spinning,” The Textile Institute Manual of Textile Technology, shortstaple spinning series, volume 4.
2. FIOMAX 1000- FIOMAX RC, “ High speed ring
spinning machine for cotton and short staple
fibres.” Sussen Technical Leaflet.
3. Shanghai Erfangji Co. Ltd, “EJM 128 Ring Spinning Machine Instruction Manual.”

About the author:

Dr. Sheikh is very senior contributor to Pakistan Textile Journal and had been contributing valuable articles in our magazines since early 1970's.

He is also a part of the faculty at Karachi based prestigious textile university (TIP- TEXTILE INSTITUTE OF PAKISTAN). His main areas of interest are spinning and nonwovens technology.