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Yarn Realization and Control of Waste in Spinning

A 1% reduction in yarn realization has almost the same economic impact on the mill’s profit as an increase on 1% in the mixing cost. This is because the resale value of wastes is much less than the price of the cotton or the yarn. The control of yarn realization is thus as important to a mill as the control of cotton and mixing cost. And yet in most mills, the approach to the control of yarn realization is half-hearted, and depends on records of dubious accuracy. In this paper, we will first consider the quantities for which records have to be maintained for estimating waste losses and yarn realization, and then give specific recommendations on how to collect data, and use them for computing accurately the mixing wise yarn realization. A simple but effective method of crosschecking the accuracy of the entire recording system will also be outlined. Norms for waste losses and yarn realization will be given mixing wise, and an appropriate procedure will be suggested for utilizing the norms for evaluating the performance of a mill.

Mr. Akash S. Bansode

D.K.T.E. Society’s Textile and Engineering Institute, Ichalkaranji - 416115.

ABSTRACT

A 1% reduction in yarn realization has almost the same economic impact on the mill’s profit as an increase on 1% in the mixing cost. This is because the resale value of wastes is much less than the price of the cotton or the yarn. The control of yarn realization is thus as important to a mill as the control of cotton and mixing cost. And yet in most mills, the approach to the control of yarn realization is half-hearted, and depends on records of dubious accuracy.

In this paper, we will first consider the quantities for which records have to be maintained for estimating waste losses and yarn realization, and then give specific recommendations on how to collect data, and use them for computing accurately the mixing wise yarn realization. A simple but effective method of crosschecking the accuracy of the entire recording system will also be outlined. Norms for waste losses and yarn realization will be given mixing wise, and an appropriate procedure will be suggested for utilizing the norms for evaluating the performance of a mill.

Keywords

Yarn Realization, Process Waste, Product Waste, Invisible Loss, Assessment of Yarn Realization, Doff Weight method, Hank Meter Reading.

1. INTRODUCTION

Yarn Realization denotes the percentage of yarn produced from a given weight of bale material. The rest is the waste which has much less worth compared to fresh fibers or yarn. In the last decade or so, the Indian mills have become acutely aware of this aspect and have introduced effective control and monitoring mechanism. The wastes are distinctly of two types:
  1. The Process waste taken out in the blow room, cards and combers which accounts for nearly 80% of the total wastes losses in cotton spinning and 50% in manmade and blends spinning. The process waste is decided by arriving at optimum levels required to achieve the desired yarn quality.
  2. The product wastes which are incurred at each stage of processing, the control over product wastes has to be exercised through effective floor supervision.
The levels should also be guided by the standards arrived at by the research associations. A 1% reduction in yarn realization has almost same economic impact on mill’s profit as increase of 1%. The records required to be maintained for waste losses and yarn realization are outlined here. Norms for waste losses and yarn realization are also given.

To have a good control on the process wastes it is important to assess the wastes in blow room, carding, comber and ring frame at regular intervals. It should be noted here that the control on wastes has to be concomitant with achieving the desired level of cleaning.
YARN REALIZATION AND CONTROL OF WASTE IN SPINNING
YARN REALIZATION AND CONTROL OF WASTE IN SPINNING



2. YARN REALIZATION

Establishment of norms for wastes is a pre-requisite for a successful waste control in a mill. Yarn realization (YR) is largely governed by the level of trash in cotton, expected yarn quality and type of machinery. Yarn Realization is governs to improve Yarn Quality, Productivity & waste reduction in process. From the SITRA paper publication achievable yarn realization can be obtained using the following formulae:

A. For mills reusing the entire usable wastes in the same mixing 

  • YR (%) = 97.5 – t – Wk – Wh for carded yarn
  • YR (%) = (100 – t – Wk) {1-(Wc/100)} – Wh – 2.5 for combed yarn

B. For mills not reusing the usable wastes in the same mixing
  • YR (%) = 97.5 – t – Wk – Wh – Wu for carded yarn 
  • YR (%) = (100 – t – Wk) {1-(Wc/100)} – Wh – Wu – 2.5 for combed yarn

Where,
t = trash in mixing (%) 
Wk = card waste (%)
Wc = comber noil (%) 
Wh = yarn waste (%)
Wu = usable waste (%)

2.1 Yarn Realization is affect by following cotton characteristics


A. Trash % in cotton purchased
Higher the trash% content in bale, higher will be need remove waste in Blow Room & lower is the Yarn Realization. Material handling storing of material in ginning process is more responsible for trash% in cotton.
B. Moisture content in cotton
As amount of moisture in cotton goes up, the yarn realization goes down.
C. Short Fiber content in material

Higher the short fiber content, higher is the removing efficiency of short fiber at comber stage because of that yarn realization become lower.
D. Departments for Yarn Realization
  • For Carded Yarn: Blow Room, Carding & Ring Frame
  • For Combed Yarn: Blow Room, Carding, Comber & Ring Frame
The control over the Yarn Realization can be done by Owner of Organization, Manager of Organization, H. O. D. of each department, Supervisors, Workers these peoples.

3. How Yarn Realization will improve?

Yarn Realization associated mainly with Cotton Feed, Yarn Produce & Waste generation. To improve yarn realization % we have to concentrate on reduction in waste generation. Better way to control over the yarn realization by means of better practical way to control over the waste generation. 

The percentage yarn realization depends primarily on process waste taken out at blow room, card & comber. Waste taken out in bow room depends on trash content of the mixing. The waste in Cards depends on type of card& also to some extent, on trash in lap. The waste in comber, depends on nature if fiber length distribution in feed.


Record to Account for Yarn Realization

Record to Account for Yarn Realization

3.1 Cotton Consumed

3.1.1 Cotton issued

In Bale form of 160 to 165 kg. 

3.1.2 Stock in process

Stock in process at various stages has to be adjusted as the weight in kg. should be multiplied by a factor:          
  • Blow Room Lap= 100/ (100-B. R. Waste %)
  • Card sliver/Drawing sliver/ Roving= 100/ {100-(B. R. waste%+ Card Waste %)}
  • Combed Yarn= 100/ {100-(B. R. waste%+ Card Waste %+comber Waste %)}

3.1.3 Waste Generate

  • The Process Waste taken out in Blow room, Cards & Combers which account for nearly 80% of total waste losses in cotton spinning & 50% manmade & blend spinning.
  • The Product wastes which are required a specified treatment at each stage of processing.
  • The Invisible loss is not directly measured. The invisible loss refers to loss caused by evaporation of moisture content in cotton, dust in atmosphere, fluff. The amount of soft waste generated in order of 6% for medium & fine count and 8-12% for coarse count.

3.1.4 Yarn Produce

The amount of Yarn Produce is measured by two methods as:
  1. Doff Weight Method: In this method the amount of yarn produce is measure by governs the weight of Empty bobbin, weight of tray & weight of full doff.
  2. Hank meter Reading: In this method the yarn produced is measured on length basis as the hank meter is attaché with front roller on ring frame.

4. Assessment of Yarn Realization

The exact assessment of Yarn Realization is not possible. Because problems associated with Assessments of:
  1. Exact amount of Fiber Feed. 
  2. Determination of exact Yarn Formed.
  3. Exact amount of Waste.

4.1 Problems associated with Assessments of Exact amount of Fiber Feed

  • Weight of bale is high so that to weigh the bale more number of laboures are required
  • The quantity of Fiber feed to process is very high it’s more than 10.000 kg/ day
  • High capacity & sensitive weight balance is required to weigh the bale of high weight which is not easily available in mill.
  • TOTAL WEIGHT of BALE = Net Weight of fiber + Weight of Packing Material.

4.2 Problems associated with Assessments of Exact amount of Waste

  • Some amount of Fiber goes in atmosphere in the form of FLUFF.
  • Moisture affects on waste amount.

4.3 Problems associated with Assessments of Determination of exact Yarn Formed

4.3.1 Limitations of Doff weight Method

  • Lot of Labour required. 
  • Transportation required.
  • Handling of Material. 
  • Exact weight of Yarn produce.

4.3.2 Limitations of Hank Meter Method

  • Accuracy of Hank Meter. 
  • Twist Contraction.
  • Idle Spindle percentage. 
  • Bonda Waste

5. Norms for Wastes &Yarn Realization


The values of all wastes are expressed as % of cotton consumed

Content
Carded
Combed
MMF
Count
4-9
10-13
14-25
26-34
28-34
35-44
45-70
71-99
-
Trash%
11
10
7
5
5
4
3
2
-
B.R. Dropping
12
11
7.7
5.4
5.4
4.4
3.2
2.2
0.1
Card waste
4.2
4.2
4.4
4.5
4.5
4.3
4.3
6.4
0.1
Comber Waste
-
-
-
-
9
10.9
12
13
-
Sweeping
2
1.8
1.6
1.4
1.4
1.2
1
1
0.5
Clearer waste
0.6
0.5
0.4
0.4
0.4
0.3
0.2
0.1
0.1
Hard waste
0.6
0.5
0.3
0.3
0.3
0.3
0.3
0.3
0.4
Invisible loss
1.8
1.7
1.6
1.5
1.5
1.3
1.3
1.3
0.3
Y. R %
78.1
79.7
83.6
86.5
77.5
77.4
77.9
77.9
97.6


Standards for Yarn Realization

Category
B. R. Waste (%)
Card waste (%)
Comber Waste (%)
Ring Frame (%)
Yarn Realization (%)
Carded Cotton Count
5 – 6
5 – 6
-
3
85 – 88
Combed Cotton Count
5 – 6
5 – 6
3 – 5
3
70 – 75
Manmade Fibers
1
1
-
2
95 – 97


6. Control on waste in spinning

To have a good control on the process waste it is important to assess the waste in Blow Room, Carding, Comber & Ring Frame at regular intervals. It should be noted here that the control on waste has to be concomitant with achieving the desired level of cleaning.

6.1 Blow Rom Waste

The cleaning at Blow Room should always be considered alongwith the following things:-
  1. The cleaning efficiency of blow room machines for, seed coats is much less than for leafy matter & sand dust taken together.
  2. The cleaning efficiency & waste increases as trash content increases.
  3. No aspect of yarn quality other than neps & foreign matter is influenced by the quality of blow room processing.
  4. An optimum level of opening is essential for cleaning of cotton.

Improving Cleaning Efficiency & Reducing waste at Blow room

To improve cleaning efficiency of beater, first examine the mechanical condition of machine, spikes on Krischner beater, blades and fingers on bladed and Porcupine openers & repair or replace as required. The inter grid bars space should be check for any chock up. The waste is affected by changes such as:
  1. Distance between the grid bars and the angle of inclination of bars.
  2. Speed of Beater.
  3. Fan speed in relation to the beater speed.
  4. Setting between feed rollers & Beaters.
  5. Setting between Beater & Grid bars.

6.2 Carding waste

The behavior of waste & cleaning at cards depends on the following considerations:
  1. The total collected waste at card does not show any close relationship with the trash in the lap feed to the card.
  2. The cleaning efficiency achieve in mills is about 80% for most mixing. However, for fine and superfine mixing for which very high flat speed and low production rates are employed, a cleaning efficiency of 85% or more is achieved. The overall effect is that the lint loss in card waste will increases with decreasing trash content in lap.
  3. There is a tendency for the card to compensate for any lack of cleaning in blow room. The overall cleaning efficiency achieve in the blow room & the card taken together remains within a narrow range of 93-95%.

Controlling the waste at Card

The following facts should be kept in mind while controlling the waste & cleaning at cards:
  1. Use of only one mote knife, placed slightly below the normal position of the top mote knife has been observed to give less waste and better cleaning in cotton mixing.
  2. Higher licker-in speed or greater wire point density on licker-in gives higher cleaning efficiency accompanied by some increase in the lint lost under the licker-in.
  3. Use of perforated undercasing helps in reducing waste.
  4. With other speeds and setting held constant, the flat strip waste varies almost proportionately with the flat speed.
  5. Wider front plate and back plate setting increase flat strip waste.
  6. For controlling cleaning of the card, almost the only place is the licker-in region.
  7. Card is excellent cleaning machine for seed coats especially the cylinder-flat region which removes 80% of the seed coats. A higher flat alongwith higher cylinder speed can be use for better removal of seed coats and also reducing neps, thick places and Classimat A & B faults. The seed coat content of 0.1% in the card sliver can be considered as satisfactory.
  8. The tandem card gives 5-7% higher cleaning efficiency and better removal of seed coats.

6.3 Comber waste

One of the main functions of combing is to remove short fibers through taking out a certain amount of comber waste. The waste thus removed also contains a large number of neps and foreign matter. Obviously, combing is not required for manmade fibers as they are free from short fibers and foreign matter. A higher % of comber waste need not always means that better removal of short fibers and neps, and therefore may not always be advantageous either for yarn quality or performance beyond a certain level.

6.3.1 Technological Consideration

For an effective removal of short fibers, retention of long fibers and removal of neps the following considerations are of up-most importance:
  1. The card trailing hooks are longer and more numerous than the leading hooks. They are removed when fed as leading hooks by keeping an even number of reversals between the cards and the comber.
  2. The waste at comber can be reduced by increasing pre-comber draft without affecting the resultant yarn quality. However, a high comber draft also result in extremely low inter fiber cohesion causing excessive lap linking, frequent sliver breaks at comber, draw frame and the can feed inter creel. Therefore, a pre-comber draft of 30-40 for counts upto 40ŝ is adequate. Pre-comber draft of above 20 is suitable only for very long staple cottons.
  3. The proper place for controlling neps is carding and no combing. It is often more economical to run cards a somewhat low production rate than to take out extra comber waste.

6.3.2 The waste at comber needs to check and controlling due to the following reasons

  1. More waste than the nominal means financial loss.
  2. Less waste than the nominal could lead to unacceptable yarn quality and performance.
  3. Comber waste variation could contribute to lea count variation.

Norms for cleaning coefficients in Blow Room


Number of Machines
Cleaning coefficients for
Seeds & Seed coats
Leafy matter & sand dust
1
0.42
0.72
2
0.50
0.80
3
0.56
0.84
4
0.60
0.87
5
0.64
0.89
6
0.66
0.90


Norms for Collected Waste & Cleaning efficiency of Card

Mixing
Trash in lap (%)
Type of card
Category of waste
Cleaning Efficiency (%)
Flat Strips
Licker-in
Others
Total
Superfine & Fine
Less than 2
SHP
2.9
1.6
0.5
4.5
88
HP
1.9
1.6
0.5
4.0
Medium & Coarse
2.0 to 2.5
SHP
2.0
2.0
0.8
4.8
83
HP
1.5
2.0
0.8
4.3
Range
1.5-2.5
1.5-2.0
0.5-1.0
4-6
85-90


Norms for Comber Waste

Warp Count Group
Level of Comber Waste (%)
28-34
7-9
35-44
11-13
46-60
12-14
61-90
13-15
91-120
14-16

6.4 Ring Frame Waste

At many stages of spinning process waste is removed to clear the cotton or to separate the short fibers but at the stage of Ring spinning there is no need to remove waste. This step is exclusively for drafting twisting and packing the yarn in the shape of bobbin. Whatsoever material is wasted here is because of our inability to control the machine, process or processing condition. Thus control the waste we have to control all factors.

At the ring frame stage a scope for saving 1.5 to 2 % on these wastes. Waste at ring frame means wastage of raw material & wastage of conversion cost upto yarn stage. If a mill spinning 20ś count, having 25000 spindles and production 205 grams/spindle at 96% spindle utilization saves 1% waste in ring frame it can save about Rs. 12 lacs per year.

6.4.1 Factors Responsible for waste generates in Ring Frame

  1. Yarn Breakage rate. 
  2. Time taken in attending to the yarn breakage.
  3. Working practice & culture. 
  4. Housekeeping & material handling.
  5. Mechanical breakdown & failures. 
  6. Methods of attending to the break downs.

6.4.2 Waste Control in Ring frame

This is done in the following steps:-
  1. Analysis and segregation of the waste of different types
  2. Weigh that waste and recording that section wise, person wise, shift wise.
  3. Comparison with the standards.
  4. Feed backs and action to improve waste generation.

7. For check & control all types waste

The following questions are helps to check and control all types of wastes:
Q. Whether a scheduled maintenance program is followed effectively?
Q. Is there cleaning of the floor can do properly?
Q. Is the material handling minimum & adequate?
Q. Whether the stocking place for cotton & yarn is good & sufficient? 
Q. Is the average yarn content per bobbin optimum?
Q. Is the proper humidity & temperature being maintained in departments?

If the above questions are put, the solution are worked out effectively implemented with the basic principles of collection of data, analysis and feed backs are followed consistently, not only that waste would be controlled also The productivity, working environment and culture all would simultaneously improve and I feel that if firmly determined every one of us is capable of controlling it.


Conclusion

In many mills, there is good scope for improving yarn realization and reducing wastes. Because in the spinning mill waste are generates in more amount & it can controllable & reducible at some extent. Improvement in yarn realization results in Rs. 3 to 10 lakhs savings per year.

The following 6 steps would be helpful to improve yarn realization:-

  1. Calculate actual yarn realization and different categories of wastes
  2. Using the formulae given in this presentation, estimate the expected yarn realization for the existing working conditions.
  3. Compare the actual yarn realization with the expected value and actual wastes with norms.
  4. Analyse the causes for deviation and initiate corrective action. 
  5. Create awareness among the workers and technical staff about the importance of waste control. 
  6. Good supervision and proper maintenance of machinery would help to reduce the waste.


References

  1. Process Control in Spinning by Gadre & Subhramanyam: ATIRA publication, page No.(45 to 107).
  2. Process Control in Spinning by Rattnam, page No. (11 to 30)
  3. Paper published by D.Shanmuganandam (Assistant Director) SITRA.
  4. Waste Control at Ring Frame by S. K. Srivastav: NITRA publication, page No. (1.1 to 1.9)
  5. Waste Investigation & Control for a Spinning Mill article in The Indian Textile Journal, September 1984 , published by, Mr. A. R. Nityanand page no.(79 to 86)
  6. A study on carding waste collection system in mill article in The Indian Textile Journal, April 2012, published by, M Muthuvelan, H Balasubramanian and A Sivaramakrishnan
  7. www.fibre2fashion.com 
  8. www.sitra.org.in

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