Critical efficiency analysis in projectile looms

S. Sudarshan

ITEMA, Service engineering, Coimbatore

sudhhan@gmail.com

P. Ganesan & S. Hariharan

Department of Textile Technology,

PSG College of Technology

ganeshg007@rediffmail.com & shariharan108@gmail.com

Abstract

Unlike in winding, warping and sizing where the emphasis ison the quality of preparation, in the loomshed, control of fabric quality aswell as of productivity assume significant importance. The weaving operationcontributes by far the largest proportion to the cost of conversion of yarninto fabric. Surveys shown that the cost of actual weaving operation in millswith modern preparatory machines and automatic looms about 65% of the totalcost for conversion of yarn into fabric.

This means that a small increase in loomshed efficiency viaproductivity will result in considerable reduction of manufacturing cost. Moreimportantly an increase in efficiency will bring in additional realization onthe extra fabric available. For a medium size average mill, an increase of 2%in loomshed productivity can increase the annual cash flow by about Rs. Sixlakhs. Consequently, in evolving a satisfactory process control programme forthe loomshed, considerable weightage should be given to efficiency.

Key words: Projectile loom, Weaving, productivity, efficiency losses.

1. Introduction

Generally, loomshed efficiency is calculated for each shifton the basis of production. In loomshed, the production is measured in terms ofeither pieces booked, metres woven or picks inserted. This method ofcalculation only gives an idea of the efficiency achieved. It does not indicatethe performance index of a mill in relation to an expected optimum. In order toknow exactly what a mill can achieve, it is necessary to have standards forefficiency losses due to various causes and a method of estimating the expectedefficiency under a given set of circumstances.

The causes for efficiency losses in looms can be dividedinto two broad categories as frequency dependent and miscellaneous. Warp andweft breaks, beam gaiting belongs to first category, where as healds broken,doffing, loom repairs, weave away, etc. are termed as miscellaneous causes.Interference is, yet, another cause of stoppage. Its extent depends upon thenumber of looms assigned to a weaver and frequency of warp and weft breaks. Miscellaneouscauses are those occurring at random. Further, such causes cannot be ascribedany definite frequency. Whenever an operator is in charge of more than onemachine, there is loss due to interference. On looms, this loss is observed tobe essentially a function of such stoppages as warp breaks, weft breaks andhence for all practical purposes, it may be expressed as a percentage of thetotal loss on account of these causes.

The efficiency losses arising from loom stoppages in loomsare generally of two types such as those requiring the weavers attention andthose not requiring weavers attention. The former category includes causeslike warp breaks, weft breaks and interference. Losses due to warp and weftbreaks are in proportion to the frequencies. The interference loss is dependupon the loom assignment to weavers, frequency of warp and weft breaks, averagedistance required to be walked per stoppage and other miscellaneous jobsperformed by a weaver. Losses due to stoppages not requiring weavers attentionarise from loom repairs, cleaning and oiling, beam gaiting and others. Efficiencyloss on account of beam change varies according to its frequency, while otherlosses depend upon the organizational setup, frequency of breakdowns, types oflooms, sorts woven and level of maintenance.

As stated earlier, efficiency losses due to warp and weftbreaks and beam gaiting of frequency dependent and hence they vary from mill tomill and also sort to sort within the same mill. On the other hand, efficiencylosses, ascribable to loom repairs, cleaning and oiling, doffing and otherstoppages are observed to be of more or less the same order between mills. Forall practical purposes, it would be quite in order to provide an overallallowance for the losses arising from these causes.

2. Characteristics of Projectile

Table 2.1 Characteristics of projectile looms

D1 is the standard steel projectile for the vast majority of commercial yarns. D12 is the same as D1 with a larger yarn clamping surface to ensure more reliable gripping ever of delicate yarns. D2 has a big cross section and large clamping surface and is used for extremely coarse yarns. K3 is the synthetic (carbon composite) Projectile which was intended to economically produce very delicate fabrics.

3. Main Features and Advantages of Projectile Weaving Machine

The main features of the Sulzer Ruti weaving machine are

• The picking and the projectile units are separated from the moving sley. The sley (Projectile track) carries the reed and griper guides.
• The gripper Projectile, made of fine steel 90mm long 14 mm wide and 6 mm thickness (3.5 in * 0.55in *0.14 in). It carries the weft thread in to the warp shed.
• The weft is drawn directly from a large, stationary cross wound package. There is no weft winding.
• The gripper Projectile is picked across the warp shed at very high speed, the picking energy being derived from the energy stored in the metal torsion bar which is twisted at predetermined amount and release to give the projectile at high rate of acceleration.
• Picking always takes place from one side, but several Projectiles are employed and all of them return to the picking side by a conveyor chain located underneath the wrap shed.
• During its flight through the shed the Projectile runs in a rack like steel guides, so that the wrap threads are touched neither by the projectile nor weft thread.
• Every pick is cut off at the picking side near the selvedge after weft insertions, leaving a length about 15mm from the edge. Similar length of weft also projects from the selvedge on the receiving side.
• The ends of weft thread projecting on both sides of the cloth are tucked into the next shed by means of a special tucking device and woven in with next pick, thus providing firm selvedges.
• The reed is not reciprocated as in a shuttle loom, but rocked about its axis by a pair of cams.
• The reed and projectile guides are stationary during pick insertion.
• The sley which carries the reed and projectile guides is moved forward and backward through a saddle carrying two follower bowls, which bear against the surface of two matched cams.
• A sley dwell of 255 at back centre enables the projectile to travel through the warp shed without being unnecessarily reciprocated by the sley.
  Whenever the reed width is reduced for weaving a small width cloth from the standard reed width, the projectile receiving unit is moved inward on the telescopic shaft, to the new selvedge position, and so the projectile travel distance is reduced.
• Smaller shed opening because of the smaller size projectile. This might result in lower warp breakage rate.
• Weft insertion rate up to 900 to 1500 m/min. is possible depending up to the width of the weaving machine.
• The colour changing mechanism is less complicated.
• There is facility of inserting two picks in the same shed without the use of a dobby.
• In case of weft breakage the take-up beam and heald frames can be driven in reverse by a pick finding mechanism.
• Two or three cloths can be woven simultaneously.
• It is possible to achieve weaving performances with breakage rates per square metre of cloth.50% of the number of breaks that would occur on a conventional loom.
• The lower warp breakage rate in a Projectile Weaving Machine may be due to

             Smaller warp shed

             Reed with higher ratio of air to wire (70:30)

             Beat up line being nearer to the centre of the reed between the two baulks.

Smaller warp shed will reduce the warp threads tension to some extent. However, care should be taken to maintain uniform tension to ensure that the warp shed is of same depth from one end to another. Otherwise a few slack warp threads at the top shed will result in stitching and end cut by the projectile.

A reed with higher ratio of air to wire will give a greater flexibility. Similarly, if the beat-up line is nearer to the centre of the reed oversized knots will pass more readily because of greater flexibility of the reed wires. In the conventional loom beat-up line is much nearer to the bottom baulk of the reed. This will result in building up higher tension of warp thread if a bigger knot of that particular thread could not pass through the reed dent, and finally the end will break.

4. Principles of Sulzer Shuttleless Weaving

The basic mechanical principles of the Sulzer shuttles weaving machine are to be considered under the following four heads:

• Picking, or weft insertion system,
• Beating-up,
• Selvedge formation, and
• Weaving with one, two, three or four colours.

In the Sulzer weaving machine, the weft yarn is introduced into the cloth by means of gripper. A tuck-in selvedge is for med by drawing the cut weft end back into the open shed by means of tucking needles. The pick is then beaten up. The sley is not moved through cranks, but is then positively rocked about its centre through a saddle carrying two follower bowls, each bearing against the surface of matched cams.

The Sulzer Shuttleless weaving machine differs from the automatic shuttle loom in two respects, namely, (a) the method of weft insertion, and (b) the method of moving the reed and projectile track. Other motions including take-up and led-off are almost similar to known mechanisms.

5. Materials and Methods

5.1 General Details

No. Of looms : 30

Weft insertion type : Projectile

Loom type : Gripper projectile

Loom make : Sulzer

Loom model : P7100

Reed width : 135 inches

Loom speed : 280 290 rpm

The object of this project is to increase the efficiency and through that increase the productivity and profitability. To do so the efficiency is analysed by various parameters such as weaver efficiency, RPM, RH%, allocation of machine, etc. After the studies the results are produced through Pareto chart for easy analysis and understanding. After that the cause and effect diagram is drawn to find the overall causes and effects for the lower efficiency.

By considering various factors the design has been produced. The design is shown below and the factors considered will help in getting very high degree of excellence in results.

6. Result and Discussion

6.1. Analysis of Efficiency by Weavers

Here we have analysed the efficiency of different weavers. By analysing we can identify the inefficient weavers as well as the idle weaver. It will help to take corrective measures on the inefficient and the guilty.

SORT 1

Table 6.1 Weavers Vs Efficiency

SORT 2

Table 6.2 Weavers Vs Efficiency

SORT 3

Table 6.3 Weavers Vs Efficiency

Many reasons contribute to the lower weavers efficiency. If one of the allocated loom stops and at the same time another allocated loom also stops then the weaver cannot able to attend both. This will decrease the loom efficiency, to reduce this, labour cooperation is needed. That is the weaver who is idle can attend the other loom.

Other causes are, if a multiple breakage occurs and at the same time another allocated loom stops, then the weaver should first attend the loom which can be restarted first. By doing this the idle time of one of the loom is reduced and efficiency is increased. The other causes following the inefficient weavers and talking with neighbors.

6.2. Analysis of Efficiency by Different Sorts

In this part we have analysed how different sorts run in the industry will affect the efficiency. Sort (design), will definitely affect the efficiency of loom. Because for each and every sort, the count of yarn will vary and number of weft yarn inserted per pick will also vary, which are having direct influence on the efficiency.

Table 6.4 Sort Vs efficiency

The efficiency of sort 3 has dropped due to multiple weft insertion, since four weft yarns are inserted at a single pick, a single thread breakage will lead to lower production. Here a small idle time will reduce the production to a greater extent. Also there is chance for higher transfer fault. For sort 3, four looms are assigned for a weaver; this will lead to higher idle time of the machine, because of higher stoppage and results in lower efficiency and production.

In sort 2 the efficiency has dropped due to higher weft breakages. This is because of poor yarn quality.

6.3. Analysis of Efficiency by Relative Humidity

Here we have analysed the relative humidity in the industry and how they affect the efficiency.

Table 6.5 Relative Humidity Vs Efficiency

The above chart shows different relation in parameters, because the international standards say that the efficiency is higher at 65% relative humidity. In this case it is upside down. This is because the standards say we have to maintain a temperature of 27^oC but in this case the industry is running at a temperature of 30.5^oC. This should be controlled to get a higher efficiency.

6.4. Analysis of Efficiency by Loom Allocation

Here we have analysed the loom allocation of the weavers. Loom allocation plays an important role in the loom efficiency. We have to be very careful here because, when more looms are allocated then there will be a problem of efficiency. When less looms are allocated then there will be a problem of wages.

SORT 1

Table 6.6 Loom allocation Vs Efficiency

SORT 2

Table 6.7 Loom allocation Vs Efficiency

SORT 3

Table 6.8 Loom allocation Vs Efficiency

This above chart also shows different relation in parameters because we can see that when lower looms are allocated the efficiency drops and when more looms are allocated the efficiency increases. While analyzing the reason this is because of the labours mischievous behaviors. When there are more labours in a place it will lead them to be more talkative and thus not attending the looms properly. To recover from this type of lower efficiency it is better recommended to keep a supervisor.

6.5. Analysis of Efficiency by Speed

Here we have analysed the speed of the loom against the efficiency. Speed of loom plays an important role in efficiency as well as productivity.

So an almost care is necessary for the analysis of the speed of the looms and their influence on the field.

Table 6.10 Speed Vs Efficiency

This has been a normal chart. Whenever there is higher loom speed it leads to higher end breakages. This will reduce the efficiency. But when you run a loom at lower speed then the productivity decreases. Higher production also plays an important role in the industries improvement. So it is recommended to run the looms at optimum speed.

6.6 Analysis of Improved Efficiency

We have given ideas from the studies taken to improve the efficiency of the industry. The chart below will show the improved efficiency

Table 6.11 Sort Vs Improved Efficiency

From the analysis which have taken, and by viewing the charts from the beginning of this chapter it evident that we can improve the efficiency of the looms. Lots of measures have been taken and the fig 4.7 shows the increase in the efficiency.

First we have advised for the supervisor for the industry, who should be there for all eight hours of the shift. It will considerably increase the efficiency. It is also very useful if rotating cameras are fixed all around the loom shed so that the efficiency will increase.

The next is the loom allocation, in sort three mainly three weavers are allocated and in sort one, four weavers are allocated. We can interchange these allocations. Because sort three is a difficult design and it is where more stoppages occur.

The weavers room atmosphere plays an important role in loom efficiency. The relative humidity and the temperature should be maintained properly and constantly to get a maximum efficiency. Whenever there is a change in these two parameters then there will be a change or drop in the efficiency.

Machine maintenance also plays an important role in the efficiency of the machine. Proper lubrication and cleaning should be done frequently. The preventive maintenance is advised for better performance of the loom

Quality of the raw material also plays an important role. When there is poor raw material, then the efficiency of the loom as well as the quality of the fabric decreases.

Motivation is another major thing to be considered. If a weaver is able to produce higher efficiency he should be encouraged by higher percentage of wages or in some other way. At the same time if a weaver produces lower efficiency the he should be punished by reducing the percentage of wage or by some other way.

Conclusion

An attempt has been made to provide an understanding of historical, technical and fundamental concepts relating to weaving and appreciation of the purpose of the whole operation. The overall object is to produce fabric of suitable quality at a cost which is acceptable. The industry is highly competitive and it is far from easy to satisfy this apparently simple objective. To do so, it is imperative that management of both man and machine should be carefully studied in order that they may give of their best.

The efficiency is analysed by various parameters. This gives a detailed idea of how the efficiency is dropped. While taking corrective action from the results analysed, we can get a higher efficiency. A small increase in efficiency will give higher productivity and profitability and that has been obtained. From the results the various factors affecting the efficiency is found and by concentrating in those areas the efficiency of the loom shed is increased. In sort 1 the efficiency has increased about 0.6%, in sort 2 it is about 2% and in sort 3 it is about 3.5%. This increase in efficiency can be achieved with small effort but for further increase we have to work hard.

REFERENCES

1. Banerjee, N.N. (1999) Weaving Mechanism, Smt. Tandra Banerjee and Apurba Banerjee, Vol.2, pp.127-158.

2. Talukdar, K.M., Sriramula, K.P. and Ajaonkar, B.D. (1998) Weaving', Mahajan, pp.344-363.

3. Lord, R.P. and Mohamed, H.M. (1988) Weaving: Conversion of Yarn to Fabric, MTL, pp.326-342.

4. Modi, C.V. (1980) Materials Control in Weaving, a Textile Association Publication, pp.158-176.

5. Greenwood, K. and Vaughan G.N. (1958) Weft Tension during Weaving, J. Text. Inst., pp.247-288

6. Estimation of Expected Efficiency on Automatic and Non-automatic looms (1974), BTRA Special Publications, pp.28-56

7. Automatic loom Efficiency (1970), BTRA Survey Report.

8. Relation of Reed Width and Cloth Width (1949), Textile Manufacturer, pp.56-98

To read more articles on Textile, Industry, Technical Textile, Dyes & Chemicals, Machinery, Fashion, Apparel, Technology, Retail, Leather, Footwear & Jewellery,  Software and General please visit https://articles.fibre2fashion.com

To promote your company, product and services via promotional article, follow this link: https://www.fibre2fashion.com/services/article-writing-service/content-promotion-services.asp