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Report | March 2017

Hard waste: A necessary evil

During processing cost reduction is strongly needed and one of the area is hard waste control.

RN Yadav presents possible hints for keeping the hard waste at minimum level in various sections of spinning, weaving and during transportation whether internal or external.

Wastage of anything is bad. Be it human, time, input, power, product or by-product. In textile industry and particularly spinning and weaving mills soft waste, hard waste and dust are main waste generated during mechanical processing of fibre and yarn to produce grey fabric. An effort is made in this paper to standardize the hard waste being necessarily generated during production.

Minimum the levels of hard waste better the productivity.

Hard waste is nothing but yarn waste produced in all departments from spinning onward. The hard waste can be classified into two varieties by origin – fixed waste and variable waste.

Fixed waste is that waste which is inherent in the very working of the process e.g., piecing waste in spinning, creeling and piecing waste in winding, warping, pirn winding, creel on sizing, knotting of beams, change of weft, pirn or cone, selvedge cutting on looms, etc.

Whereas variable waste arises on account of spoilages and poor performance of operators, process materials, process parameters and machines. Such type of classification helps in controlling hard waste. Proper care during material handling, good house-keeping and regular training of operatives are always helpful to control variable hard waste.

Maintaining a detailed record of hard waste section-wise, machine-wise and operator-wise in each shift of production helps a lot to act and minimise hard waste. Mind set is the only basic element to establish norms for different section for cotton and synthetic material being processed in spinning and weaving sections. Various research institutions like ATIRA, BTRA, NITRA, SITRA, etc. have done a lot of research work and guided mill personnel in reducing hard waste and improving productivity. Even 0.01 per cent reduction in hard waste has impact on balance sheet of medium and large size mills making difference of lakhs of rupees. Reduction of hard waste is possible by working on:

  • Technicals – Concerning machine and process parameters.
  • Operations – Improving skill of operatives by training, re-training time-to-time on various types of machines.
  • Ambient condition of departments must be always in comfort zone having requisite moisture content in air, preferably 12-15 gm/M3 in cotton and blend spinning and 14-19 gm/M3 in weaving
  • section. Comfort zone condition means temperature near room temperature and never above human body temperature and related humidity near pleasant to body feel.

Hard waste generation

Basic causes of hard waste generation are mentioned below –

  • Ring Frame - while piecing broken ends.
  • Winding/Autoconer – while knotting/splicing cut ends due to fault clearing and cop change.
  • Assemby/TFO/Doubler – while creeling/knotting/splicing.
  • Reeling – for hank forming from ring cops, doubler cops, cones, cheese, etc.
  • During unwinding/winding of dyed yarn from cheeses or cones.
  • Warping – taking ends for warp sheet forming, jointing broken ends etc.
  • Pirn winding – jointing broken ends, defective pirns.
  • Sizing – drawing warp sheets, entanglements.
  • Drawing & Knotting – ends drawn length, entanglements, Knotting ends.
  • Loom – beam gaiting/knotiing, last warp sheets, selvedge, fringe cut yarns, extra warp yarn.
  • Grey folding – clippings, mendings.

Spinning

Ring frame tenter should not make bad piecing, either long ends from front roller nip or from back of delivery cot, generally known as over piecing. Short and long thick places are produced by such bad operational practices result in cut at winding stage and so hard waste generation. Slough-offs and top/bottom spoilage of ring cops should not be at all. On new generation ring frame tail end must be correctly adjusted as per yarn fineness and starting spindle speed. Ring cop yarn quality must be nearly fault-free. Sometimes long thick and thin places in yarn are being created due to double roving fed by operator at inter, ring-frame creel or during manual creel change by ring-frame tenter.

Winding

The winding section contributes substantially to over all hard waste around 60 per cent in yarn forming mill and 20 percent in composite mill. Bad bobbins and bad cones contribute to most of the hard waste. Where yarn dyeing or doubling is involved, it will further increase the hard waste generation.

The reasons for hard waste at winding stage are as under and corrective action needed technically, mechanically and operationally to reduce the hard waste generation. The reasons are: winding attendant rejecting bottoms, double gaiting and thick yarns, damaged bobbins surface, fine yarns, soft yarn, ring-cut, anti-balloon ring-cut, spoiled doffs, overfilled doffs, etc., winding drum defects, more cuts at winding stage. As a norm, winding cuts should be below the yarn count, Ne. For example, winding cuts 60 in case of 60s count, 30 in case of 30s count and so, material handling and bad storing condition.

Warping

The reasons of hard waste generation at warping stage consist of following elements: damaged package; package fault like bottom stitches, ribbons, too hard package or too soft package causing unwinding problems and slough-offs respectively; weak yarn causing end breaks; creel boy taking too much yarn from package while creeling; variation in creel tension, causing loose/tight ends; rough warp beam surface, beam flange not correctly set; warp sheet not correctly matched in the comb; improper mending of broken ends; and preventive and corrective actions are very much needed to control hard waste.

Some of the points are: average yarn tension should be adjusted according to yarn count within 5 percent of the single thread strength of the yarn; beam density should be correct and beam size maximum possible; ambient conditions should be correctly maintained; perfect preventive maintenance and a good house-keeping is must; concentricity of beam-flange be assured; stop-motion and brakes be fully effective; yarn on the beam should not have any frictional damage right from creel package to beam formation point; the length of yarn sheet that can be accommodated on the warper’s beam should not be too low – otherwise there will be large increase in hard waste; the set length has to be kept the same on all the common beams; warp beam should not have damaged flange or bent shaft; and all the warp breaks should be tied with same warp ends or otherwise it will lead to lappers and migration of ends during sizing causing hard waste generation.

Sizing

Following are the requisite to minimise the hard waste in sizing and afterwards –

  • Excess lappers and migration ends.
  • Performance of size yarn be up-to norm & above.
  • Sizing ingredients and process, if uncontrolled loom breaks occurrence becomes high, particular warp-wise.
  • Size fall on loom be minimum, again to reduce breaks.
  • Size beam flange must be concentric and undamaged.
  • Uniform tension from end to end.
  • Ends wound on must be straight and parallel to each other, with no rolled, crossed, stuck or lost ends.
  • Uniform warp density throughout the sized beam.
  • Selvedge ends not high or low but flat with the warp.
  • Uniform application of the size.

Preventive & corrective measures during sizing

  • Warper beams having the same yarn length or multiple of it should be selected to form a set for sizing. This will reduce hard waste at grey stage.
  • Damaged warping beams should not be used as it will lead to problem of lappers during sizing.
  • Size preparation, proper ingredient and mixing, size adds on and proper process control must to minimise sized yarn waste.
  • No sticky sizing at all. Proper size process parameters be there to deliver 1st layer to last layer for standard size beam functionality.

Non-automatic looms:

The reasons for hard waste generation are weft bottom, defective pirns, extra ends, floats, shuttle smashes and tail ends.

Weft bottom can be reduced by proper alignment of pirns, reducing the weft breaks at the end of pirn. Extra ends can be reduced by controlling the lappers at the sizing. Carelessness by drawers and knotters is also a cause of extra ends. Proper loom settings and good house keeping can reduce the incidence of floats. Tail end, which is the length of yarn remaining on the loom, is from weaver to breast beam. When the beam is exhausted, it should not exceed two meters.

And the most important, standard ambient conditions must be maintained.

Automatic looms

Main reasons for hard waste generation are control of the quality of yarn and package, control of warp and weft breakages, efficient house-keeping, and standard ambient conditions.

And to control

  • Battery filler doesn’t unwind more than fifty centimeter of yarn while creeling.
  • Yarn length on reserve should be just enough for five picks.
  • Proper functioning of filler motion.
  • No more extra ends. Extra ends should be hardly one end for 1,000 ends in warp.
  • Loom tail not more than two metres.
  • Material handling equipments and storage system be correct.
  • Proper ambient condition in comfort zone be maintained.

What should be amount of hard waste?

Records for hard waste generation and control were collected for a continuous period of six years in a composite mills working on cotton, synthetic and blended yarn and cloth manufacturing and the norms were established scientifically taking into account of various facts of technical and operational elements.

Below is summarised norms and super norms regarding hard waste generation in terms of percentage of production. Super norms are applicable for fully automatic and under control operational mills.

Conclusion

Hard waste is a necessary evil. Reduce it to the level of necessary and finish evil. That means allow only technically needed generation and limit it by complete control on operational bad habits.

The article is authored by RN Yadav, who is President of The Rai Saheb Rekhchand Mohota Spinning and Weaving Mills Ltd, which is located at Hinganghat - 442301, Wardha (M.S) district. RN Yadav can be contacted at: Email: president@rsrmm.com

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