A Study on the Eff ect of Pin Density on Stationary Flats and its Setting on Carding Quality

Carding is the most vital process in spinning, which infl uences the sliver quality and the resulting yarn characteristics. The eff ect of carding on single fi bre and bundle fi bre properties were studied by employing advanced fi bre information system (AFIS) and diff erences in properties are reported. For a good quality yarn, the process parameters and setting in the carding are needed to be selected properly. The paper presents the results due to the eff ect of points per square inch (PPSI) in stationary fl ats of licker-in side (SFL). The effect of setting between the fl ats and cylinder was also studied. The sample was prepared using LMW spinning line using LC-333 carding machine. After regulatory changing the PPSI in SFL, the neps in the carded sliver were reduced. The experimentation led to the reductions in the total imperfection in yarn.


Introduction
Th e process of converting fi bre tuft s into sliver involves processing over several zones in a carding machine.Th e fi rst zone is a feeding zone which involves feeding section of the carding machine.In the feeding zone, fi bre tuft s are fed into the carding machine by means of two methods: one is via a lap-sheet feeding and the other is via a chute feed [1].Th e method used for study in this research paper deals with the chute feed system.Aft er getting through the feeding zone, fi bre tuft s come under the action of licker-in, and from there, they enter into a carding section.Th e activity in the carding section is observed and analysed for the purpose of the study.Carding action can be described as the combing of fibres between two wired surfaces (card clothing), oriented in opposing directions, with their relative speed greater than zero.Th is action individualises the fi bres and gives parallelism to the fi bre mass fl ow [2].Carding machine performs the following task: opening of individual fi bres, elimination of impurities, Madan Lal Regar, Niharika Aikat Dr. B R Ambedkar National Institute of Technology, Jalandhar Punjab -144011, India

Izvleček
Mikanje je najpomembnejši postopek predenja, ki vpliva na kakovost pramena in s tem na lastnosti preje.Vpliv mikanja tako na lastnosti posamičnega vlakna kot na lastnosti snopičev vlaken v kopreni smo raziskovali s pomočjo naprednega informacijskega sistema (AFIS); razlike v lastnostih predstavljamo v članku.Za dobro kakovost preje je potrebno skrbno izbrati procesne parametre in nastavitve mikanja.V članku so predstavljeni rezultati raziskovanja vpliva gostote obloge mikalnih pokrovčkov (PPSI: število zobcev na kvadratnem inču) na stacionarnih mikalnih pokrovčkih rahljalnega valja.Proučili smo tudi vpliv nastavitve med mikalnimi pokrovčki in valjem.Vzorec smo pripravili na predilni liniji LMW z uporabo mikalnega stroja LC-333.Po spremembi PPSI na SFL se je število vozličkov (nopkov) v mikanem pramenu zmanjšalo.S pomočjo eksperimentov smo zmanjšali skupne nepravilnosti v preji.Ključne besede: mikanje, gostota obloge na stacionarnih mikalnih pokrovčkih, PPSI, nopki, neenakomernost preje elimination of dust, disentangling of neps, elimination of short fi bres, fi bre blending, fi bre orientation and sliver formation.Th e number of neps increases from machine to machine in the blow-room, the card reduces the remaining number to a small fraction.Improvement in disentangling of neps is obtained by a closer spacing between clothing, sharper clothing, optimal speed of licker-in, low doff er speeds, lower throughput.To achieve a good quality of carded sliver, the pre-carding, carding and postcarding operations are important [3]."Th e card is the heart of the spinning mill" and "Well carded is half spun" are two well-known proverbs of the experts.Th ese proverbs apprise the immense signifi cance of carding in the spinning process [4,5].Th e carding quality is primarily determined in the cylinder region, where the revolving fl at is of high importance [6].With an optimal number of fl at bars, it is responsible for cleaning as well as extracting neps and short fi bres.Th e purpose of highspeed carding is to increase the card productivity without reducing carding quality or even improving it to some extent.However, it had been assumed that increasing the carding speed would also increase the fi bre breakage [7].High production carding machine economises the spinning process and leads to the reduction in yarn quality.Hence, higher the rate of production, the more sensitive becomes the carding operation and the greater is the danger of a negative infl uence on quality.Since 1965, the production rate has been increased from about 5 kg/h to about 100 kg/h, a rate of increase not matched by any other machine except the draw frame.Th e technological changes that have taken place in the process of carding are remarkable compared to any other technology in textile processing [8,9].Th e opening or individualization of fi bres achieved by the carding action between the cylinder and fl ats is expressed by the number of wire points [10].With an increase in the production rate in carding, the points per fi bre decrease leading to the reduction of the carding action.In the carding zone, if any fi bre bundle is not opened up in the fi rst few fl ats, it is diffi cult to open it in the last fl ats.Th e rolling action after the 5 th fl at or so, when no more carding is possible and leads to neps formation.Th is defi ciency can be rectifi ed by the following: increase in wire point density increase in cylinder speed increase in carding surface -Th e increase in the density of wire points in cylinder and the increase in the speed of cylinder have certain limitations, both technologically and mechanically.Th e only possibility is to increase the carding surface or changing the carding position.Aft er some prior researches in this fi eld, it was found that the increase in carding surface could be considered as the best alternative.Th erefore, it seems to be the creation of additional carding position or introduction of the stationary fl ats of lickerin side (SFL) and stationary fl ats of doff er side (SFD).By introducing SFL, the pre-carding action has been substantially improved.Modern carding machines are equipped with several stationary fl ats of licker-in side (Fig. 1).Th e SFL encounters tuft s.Th e setting should be close enough so that the fi bre tuft s get pre-carded thoroughly before reaching the fl ats.It leads to the liberation of dust and short fi bres which are immediately sucked away.

Figure 1: Side view of LC-333 (left : zoomed view of stationary fl ats of licker-in side)
Th e setting in the pre-carding zone has a strong infl uence on nep level, cleanliness and short fi bre level.If the pre-carding action is better, then it will reduce the cylinder load resulting in better carding action on fi bre.Th e carding action also depends upon the setting between the cylinders and fl ats.Th e setting between the cylinder and fl at is optimum for the quality of fi bre (fi bre fi neness, dust level, tenacity) over the entire fl at zone, the setting is gradually reduced in the material fl ow direction in order to gradually increase the intensity of opening [11,12].If the setting is too close, it would lead to the thorough opening of fi bres with the liberation of dust and trash, but neps and short fi bre may increase due to higher stress on fibres.Th e yarn neppiness is infl uenced by the number of neps in the raw material [13].As the PPSI (points per square inch)1 is increased on the cylinder, the nep removal effi ciency also increases [15].Th e reduction Setting on Carding Quality Tekstilec, 2017, 60 (1), 58-64 in card sliver neps with variable density cylinder wires is fully refl ected in the quality of corresponding yarns.Th e nep removal effi ciency of card increases with the sharpness of fl at and cylinder wires.New (sharper) wires were found to produce slivers with fewer neps [14,15].Th e present paper studies the eff ect by changing the point per square inch in stationary fl ats of licker-in side and the observations are analysed.Th e mechanical properties of the yarns before and aft er changing the SFL and gauge setting is an area for future work and this study has been limited and focused on physical properties.

Material
Th e properties of the fi bres used to produce the yarn are given below in Tab. 1.For the yarn samples preparation, the following process parameters were used (Tab.2).
Carding setting parameter PPSI of SFL was changed in carding machine (Tab.3).

Testing methods
Th e yarns were conditioned at the standard tropical atmospheric condition of 65±2% RH and 27±2 o C temperature for 24 hours.Th e number of tests for each parameter were taken to ensure the result to attain 95% confi dence limit.

Neps
Th e neps study was carried out on the advanced fibre information system (AFIS).For neps testing, 100 gm of fi bre sample were taken from the feed material on carding, the same amount of sliver sample was taken aft er the carding operation.

Nep removal effi ciency
Th e parameter characterising the carding machine eff ectiveness in the aspect of nep reduction is the Nep Removal Effi ciency (NRE), which is expressed by the equation:

Unevenness and imperfection
Th e evenness was measured on Uster Evenness Tester-5, which simultaneously measures the hairiness and imperfections.Yarn imperfections refer to the total number of thin places (-50%), thick places (+50%) and neps (+200%) present per 1000 metre of yarn.

Results and discussion
Th e number of neps/gram in sliver, unevenness and imperfection values of the yarns are given in Tab. 4. Th e yarn is produced before and aft er changing the SFL and gauge setting.

Eff ect of SFL PPSI and gauge setting on sliver properties
Stationary fl ats in licker-in side and doff er side are the recent introductions in the spinning industry for improving card sliver quality.Th e graphical representation of the eff ect of carding delivery speed and SFL PPSI on neps, short fi bre content (SFC), and NRE in sliver are shown in Fig. 2.
It is inferred from the graph (Fig. 2a) that the neps per grams in sliver are reduced aft er reducing the point per square inch on SFL.Th e chances of fi bre damage increase when the number of wire points on SFL increases hence more will be the nep formation.Th e point per square inch on the 1 st set of the plate in SFL side is reduced from 140, 140 to 90, 140.With this particular experimental setup, the fibre is initially in contact with a lesser contact point so the opening of tuft s started and then from the 2 nd plate, the points per fi bre increased.Similarly, PPSI in the 2 nd set of SFL is changed from (240, 240, 240 to 90, 140, 140) and in the 3 rd set of SFL 340, 340, 340 to 240, 240, 240.Th e feeding of fi bres to the carding zone increases with increase in the card delivery rate.Th is, in turn, aff ects the carding action as with an increase in input fi bres, the number of fi bres per wire point is increased.Hence the resulting neps per grams are increased by increasing the delivery speed.Th e Short Fibre Content is defi ned as the percentage of fi bres less than 12.7 mm in length.It is again inferred from Fig. 2b that the SFC/grams have reduced with the change in the setting in the precarding zone.Before the change in PPSI on SFL plats, the seed fi bre coat is more due to similar points per square inch on tuft s.When a fi bre enters the pre-carding zone, the opening up operation may suff er due to a similar trend of wire density.As a result, the points per square are reduced resulting in the better opening up.It is evident from Fig. 2 that with an increase in the delivery speed, a short fi bre content tends to increase in the card sliver.Th is is  due to fi bre breakage at higher tensions.It is likely that when the fl at's speed is kept constant, the fi bres are stretched by the higher doff er speed which results in maximum fi bre breakage.It is also inferred from Fig. 2c that the nep removal effi ciency (NRE) is increased aft er the change in pre-carding setting and PPSI on SFL with respect to carding delivery.Neps are created by the mechanical handling, cleaning of the cotton fi bre.Neps increase throughout the ginning, opening and cleaning process.Th e nep removal effi ciency depends on the number of neps present in a feed fi bre and settings in carding.Aft er changing the SFL and its setting, it directly infl uences the NRE.Th e NRE decreases with increase in the delivery speed of carding.When the delivery speed is increased, it reduces the time for the carding operation and hence due to the reduction in time, the neps could not be opened up properly.Th e formation of neps may also be possible due to high speed.

Eff ect of SFL PPSI and gauge setting on yarn properties
Th e raw materials and the technological process infl uence the fi nal yarn quality.Th e graphical representation of the eff ect of carding delivery speed and SFL PPSI on unevenness, total IPI, and hairiness of yarn are shown in Fig. 3. Th e value of unevenness, U, and total imperfection are also shown in Tab. 4. Fig. 3a depicts the eff ect of PPSI of SFL and card delivery rate on yarn unevenness.It is clear from Fig. 3a that yarn unevenness decreases aft er changing the PPSI of SFL.As the points per square inch of the stationary fl at are reduced, the opening up of neps is better in the pre-carding zone and hence it is directly refl ected in the fi nal yarn properties.It is also evident from Fig. 3a that yarn unevenness increases with an increase in the delivery rate of the card.As the card delivery rate is increased from 160 to 170 m/min, there is a steady increase in the yarn unevenness (U) from an average value of 9.07 at 160 m/min delivery rate to 9.6 at 170 m/min delivery rate.Th e trend indicates that the yarn unevenness is directly proportional to the card delivery.Th e trend in the result can be explained as follows: the higher delivery rate results in poor carding, higher cylinder loading and more leading fi bre-hooks in the carded sliver.Ultimately, roving with higher leading fi bre-hooks is forwarded to the ring frame contributing to an increase in yarn unevenness.Fig. 3b depicts the eff ect of PPSI of SFL and card delivery rate on total imperfection.Th ere is a tremendous reduction (139 to 67 at 160m/min) in total imperfection aft er the change in points per square inch of SFL.Th e decrease in the total imperfections with the decrease in points per square inch of SFL can be explained by good pre-carding and nep removal at the carding stage.A yarn with the higher number of yarn imperfections will ultimately result in poor fabric appearance.Th e points per square inch of SFL is playing the vital role in the pre-carding zone.As discussed earlier, the similar trend of wire density is not improving the sliver quality and by avoiding the similar trend the nep removal effi ciency is increased and ultimately its reduces the total imperfection.Mean plot depicting the eff ect of card delivery rate and PPSI of SFL on yarn hairiness are given in Fig. 3c.It is inferred from the Fig. 3c that yarn hairiness increases with the increase in card delivery and it also reduces aft er reducing the wire density on SFL.Th e average hairiness before the change in wire point density was 4.94 at 160m/min and aft er the change, the hairiness is reduced to 4.92 at the same delivery speed.Th e diff erence between before and aft er the change of hairiness is not so great at 160m/min but the diff erence is high for 180m/min.Th e yarns with high hairiness may result in a greater amount of fabric pilling and surface fuzziness as compared to the yarns with lower hairiness.

Conclusion
Th e analysis of the study presents an overview of the eff ect of changing the point per square inch in stationary fl ats of licker-in side (SFL) on sliver and yarn properties.It has been found that by reducing the point per square inch in stationary fl ats of licker-in side (SFL), the number of neps per grams in sliver is reduced.Also, the SFC/grams has decreased with the change in the setting in the pre-carding zone.Th e yarn unevenness was found to be directly proportional to the card delivery rate.Th e increase in the card delivery rate results in poor carding since it leads to higher cylinder loading and more leading fi bre-hooks in the carded sliver.A considerable reduction in total imperfection was found with the decrease in points per square inch of SFL.Further, the reduction in yarn hairiness was Setting on Carding Quality Tekstilec, 2017, 60 (1), 58-64 found with the reduction in pin density on SFL at diff erent rates of card delivery speed.Th e results obtained on the basis of experimentation may be used in a customised yarn production for diff erent applicability.Even various customization may be achieved automatically by programming the carding mechanisation.Th e programmable design of such mechanisation can be obtained by suitable hardware and soft ware interaction that has not been dealt in the paper.However, the prospect of such design can be investigated further in the future course of action.Th e mechanical properties of the yarns before and aft er changing the SFL and gauge setting is an area for the future work and this study has been limited and focused on physical properties.

Table 1 :
Specifi cation of fi bre used

Table 3 :
Carding setting parameters a) Before changing the PPSI on SFL and gauge setting b) After changing the PPSI on SFL and gauge setting

Table 2 :
Process parameters for yarn production NRE is nep removal effi ciency, Nep Cnt/g feed is the nep number per gram in fi bre stream feeding the machine and Nep Cnt/g delivery is the nep number per gram in the fi stream delivered by the machine.

Table 4
Eff ect of changing the PPSI on SFL, gauge setting and delivery speed on yarn and sliver properties a) Before changing the PPSI on SFL and gauge setting b) Aft er changing the PPSI on SFL and gauge setting Setting on Carding Quality Tekstilec, 2017, 60(1), 58-64