I Indian Journal of Textile Research Vol. 9, June 1984, pp. 38-45 Setting Limits for Twill Woven Fabrics I C SHARMA, H R SHARMA, SUKESH SHARMA, HARISH KUMAR & ANUP GARG The Technological Institute of Textiles, Bhiwani 125022 Received II July 1983; accepted II November 1983 A method of arriving at the square setting of woven fabrics is reported. An attempt has been made to relate cloth setting limits with the rate of fabric production (the rate of production decreases as weft density in the fabric increases) as controlled in the case of negative let-off motion during weaving. Taking the existing cloth setting theory to be applicable in mill practice, a criterion for comparing settS has been evolved and a possible practical relationship fot obtaining the maximum practical loom sett in the case of twill woven fabrics is deduced. Samples have been woven using 72', 80' and 88' reeds, in each case running a series of different weft setts, reaching up to the maximum possible setL Three weft cotton counts, 2/20', 2/40' and 2/60', with 2{40' warp count (polyester-viscose blend for each 48/52) were used. Six right hand twill weave structures (2/2, 211/121, 3/3, 4/4, 3(5 and 2/6) were wo~en. In each case, the cloth-fell distance was also measured on the loom during weaving. In all the cases, limits for maximum setts have been determined and the values compared with those obtained by Law [Wool Rec Text Wld,21 n922) 968] and Brierley [Text Mfr, 57 (1931) 3; 58 (1932) 178,342; 78 (1952) 349, 431,437,449,595; 79 (1953) 71, 189,293]. Different cloth setting theories and rules for estimating maximpm threads per inch in woven fabric have been proposed! -4. These theories are based either on the geometrical representation of fabric construction or on the experimental work carried out for the purpose. Geometrical representation of fabric construction is complifated,ebecause fibres, yarns, fabric construction and i~terlaced threads do not follow definite geome~rical shapes and. forms. Threads when interlaced in woven fabrics are not circular in cross- section, but are distorted and flattened considerably. In certain woven structures, the threads tend to group and overlap, so that a simple geometry, even if the threads were of a regular shaped cross-section, would be complicated. Practical limit for threads/in, obtained experimentally, is the most appropriate criterion, as it provides to the manufacturer information regarding the production technique to be adopted. Hence, this approach was used in the present work. When the count of yarn and number of threads per unit length in warp and weft are the same, the structures are called balanced or square built structuf.es. When the warp to weft count and/or sett differ, the structure is said to be unbalanced in count and/orsett respectively. Considerable work has been carried out at the Leeds University9 on the limits of sett (both balanced and unbalanceq) that can be woven in various weave structures (plain, twills, sateens, etc.) and it has been observed that relationships between relative weave value ahd unbalanced sett quoted in the various setting theories are not always correct. Most of the results of these workers regarding weave values and the estimation of square sett are in agreement. Their results regarding unbalanced setts vary according to 38 the class of weave, average float and the square sett about which the unbalancing takes place, while the rules of LawS and Brierley6 apply for unbalanced sett, irrespective of the class of weave, average float, etc. H was considered worth while to carry out experiments on twill weave structure, since it has not been investigated so far. Materials and Methods Warp of 2/408 cotton count and wefts of three different counts, viz. 2/20" 2/408 and 2/608,having the same polyester-viscose blend proportion (48: 52) were used. A warp sheet of 4200 ends was given 8% size, with a stretch of 1% on an Indequip sizing machine (Ahmedabad). Drawing-in was done on 8 healds in the straight order of 1-2-3-4-5-6-7-8 with 2 ends/dent. Weaver's beam was gaited on Cimmco Gwalior non- automatic loom fitted with dobby, having 72 in reed space, 48 in beam width and running at 122 rpm. The loom was fitted with 7-wheel intermittent positive take-up motion, loose reed motion, over-pick motion, side weft fork motion and spiked ring temples. The loom was also fitted with negative let-off motion. For weft preparation, Hacoba Kavery fully automatic pirn winder with a spindle speed of 6000 rpm was used. By using different peg plans, lattices for 2/2, 211/121,3/3,4/4,3/5 and 2/6 twill weaves were woven. For each weave, three differ~nt weft counts (2/20" 2/408and 2/608)and three reeds (72" 808and 888)were taken, in each case running a series of weft setts, reaching up to the maximum possible sett. The timings of the various motions of the loom relative to crank top centre as zero were as follows: o or 360o-Healds in level, sley in mid position between back and front centres, T
Transcript
I
Indian Journal of Textile Research
Vol. 9, June 1984, pp. 38-45
Setting Limits for Twill Woven Fabrics
I C SHARMA, H R SHARMA, SUKESH SHARMA, HARISH KUMAR & ANUP GARG
The Technological Institute of Textiles, Bhiwani 125022
Received II July 1983; accepted II November 1983
A method of arriving at the square setting of woven fabrics is reported. An attempt has been made to relate cloth settinglimits with the rate of fabric production (the rate of production decreases as weft density in the fabric increases) as controlled inthe case of negative let-off motion during weaving. Taking the existing cloth setting theory to be applicable in mill practice, acriterion for comparing settShas been evolved and a possible practical relationship fot obtaining the maximum practical loomsett in the case of twill woven fabrics is deduced. Samples have been woven using 72', 80' and 88' reeds, in each case running aseries of different weft setts, reaching up to the maximum possible setL Three weft cotton counts, 2/20', 2/40' and 2/60', with
2{40'warp count (polyester-viscose blend for each 48/52) were used. Six right hand twill weave structures (2/2, 211/121, 3/3, 4/4,3(5 and 2/6) were wo~en. In each case, the cloth-fell distance was also measured on the loom during weaving. In all the cases,limits for maximum setts have been determined and the values compared with those obtained by Law [Wool Rec Text Wld,21n922) 968] and Brierley [Text Mfr, 57 (1931) 3;58 (1932) 178,342; 78 (1952) 349, 431,437,449,595; 79 (1953) 71, 189,293].
Different cloth setting theories and rules for estimatingmaximpm threads per inch in woven fabric have beenproposed! -4. These theories are based either on thegeometrical representation of fabric construction oron the experimental work carried out for the purpose.Geometrical representation of fabric construction is
complifated,ebecause fibres, yarns, fabric constructionand i~terlaced threads do not follow definitegeome~rical shapes and. forms. Threads wheninterlaced in woven fabrics are not circular in crosssection, but are distorted and flattened considerably.In certain woven structures, the threads tend to groupand overlap, so that a simple geometry, even if thethreads were of a regular shaped cross-section, wouldbe complicated. Practical limit for threads/in, obtainedexperimentally, is the most appropriate criterion, as itprovides to the manufacturer information regardingthe production technique to be adopted. Hence, thisapproach was used in the present work.
When the count of yarn and number of threads perunit length in warp and weft are the same, thestructures are called balanced or square builtstructuf.es. When the warp to weft count and/or settdiffer, the structure is said to be unbalanced in countand/orsett respectively.
Considerable work has been carried out at the LeedsUniversity9 on the limits of sett (both balanced andunbalanceq) that can be woven in various weavestructures (plain, twills, sateens, etc.) and it has beenobserved that relationships between relative weavevalue ahd unbalanced sett quoted in the various settingtheories are not always correct. Most of the results ofthese workers regarding weave values and the
estimation of square sett are in agreement. Theirresults regarding unbalanced setts vary according to
38
the class of weave, average float and the square settabout which the unbalancing takes place, while therules of LawS and Brierley6 apply for unbalanced sett,irrespective of the class of weave, average float, etc.
H was considered worth while to carry outexperiments on twill weave structure, since it has notbeen investigated so far.
Materials and MethodsWarp of 2/408 cotton count and wefts of three
different counts, viz. 2/20" 2/408and 2/608,having thesame polyester-viscose blend proportion (48:52) wereused. A warp sheet of 4200 ends was given 8%size, witha stretch of 1% on an Indequip sizing machine(Ahmedabad). Drawing-in was done on 8 healds in thestraight order of 1-2-3-4-5-6-7-8 with 2 ends/dent.Weaver's beam was gaited on Cimmco Gwalior nonautomatic loom fitted with dobby, having 72 in reedspace, 48 in beam width and running at 122 rpm. Theloom was fitted with 7-wheel intermittent positivetake-up motion, loose reed motion, over-pick motion,side weft fork motion and spiked ring temples. Theloom was also fitted with negative let-off motion. Forweft preparation, Hacoba Kavery fully automatic pirnwinder with a spindle speed of 6000 rpm was used.
By using different peg plans, lattices for 2/2,211/121,3/3,4/4,3/5 and 2/6 twill weaves were woven.
For each weave, three differ~nt weft counts (2/20"2/408and 2/608)and three reeds (72" 808and 888)weretaken, in each case running a series of weft setts,reaching up to the maximum possible sett. The timingsof the various motions of the loom relative to crank topcentre as zero were as follows:
o or 360o-Healds in level, sley in mid positionbetween back and front centres,
T
SHARMA et at.: SETTING LIMITS FOR TWILL WOVEN FABRICS
90°-Crank on front centre, reed in contact withcloth, beat-up,
120°-Shed or healds open, dwell period onshedding commences,
120 to 240°-Shed open, dwell period OIl sheddingtappet,
180°-Crank at bottom centre, shuttle moves in thebox,
210°-Shuttle enters the shed,2400-Healds begin to close,270°-Shed closing, slowest movement of sley,300°-Shuttle enters the box,3300--Shuttle checked by the check strap.The displacement of fabric was measured with the
help of a linear displacement transducer (A-0415 B,New Engineering Enterprises, Roorkee, rangemultiplier XI 10, overall accuracy ±0.1% ± 1, digitaland pick up excitation 2 volts rms (5 kHz). The fullstroke range of the transducer was ± 5mm. Anattachment having a micrometer screw gauge withmagnetic head was provided. Displacement of theorder of 0.0001 mm (0.1 /l) could be measured.
Measurement of shed-Measurements were madewith the loom at rest, the crank at back centre, and theback rest in its normal position. The distance fromcloth-fell to top of back rest was 99.5 cm, cloth-fell toheald eyes of front shaft, 30cm and cloth-fell to.topwarp shed of front heald at reed at back centre, 8cm.
Measurement of fell position-Fell-creep distancewas measured by taking a permanent fixed referenceline on the breast beam. The distance between thereference line and the reed at front centre was
measured, which is always same for a loom. The loomwas stopped at the back centre, keeping the front healdraised, and the distance between the reference line andthe last pick of weft was measured. The differencebetween the two was taken as the fell-creep distanceand was noted in each case.
Warp tension-The load arranged on the leverdepends upon the count of yarn, number of threads inwarp and the weaving difficulty, i.e. difficultyencountered by a loom while beating the pick in thefabric. This is dependent on the count of yarn, threads/in in warp and weft directions, threads interlacing andloom tuning. It is also affected slightly by the yarnfriction against the reed, healds and back rest.
If the warp tension is lower than it ought to be, thebeat-up tension is insufficient to force the pick into thecloth without buckling at the beat-up. Normally, itwould be expected that the beat-up force requiredshould increase with increase in picks/in, otherconditions remaining the same. This increased beat-upforce could come only from the increased warptension.
The maximum available weft sett for any given warp
sett depends on the tension in the warp yarn. It was,therefore, necessary to arrange a warp tension whichcould give a normal fell-creep distance. The fell-creepdistance, which is governed by the tension on the warp,can be varied by changing the weight or modifying itsposition relative to the fulcrum of the lever. Therefore,it can be taken as an indirect method of measuring thetotal warp tension. A load of 1850 in Ib was found togive normal weaving. Tensiometer was used to recordthe length of 50 threads on the top and 50 threads onbottom shed; these threads were made with thecrankshaft at back centre position and the shed fullyopen. The average single thread warp tension was 95 g.
Measurement of fabric displacement-The rate ofproduction of fabric can also be measured in terms offabric displacement, as fabric production is related tofabric displacement. If the production is more, thendisplacement will be more and vice versa. In thepresent study, fabric displacement was measured usinga linear displacement transducer attached with adigital indicator. This transducer can displace only10mm of fabric. Hence, the maximum range ofmeasuring the displacement offabric was only 10mm.The loom speed and picks/in of the fabric decide thefabric production or displacement, as also the time inwhich the displacement of fabric will be 10mm. Thedisplacement of fabric was measured in this time.Suppose the loom speed is 122 rpm and picks/in 40,then the displacement of fabric will be 77.47 mm/minor 1.2911 mm/sec or 7.74 seconds are required for10mm fabric displacement. Hence, we can take thetime 7 sec for measuring the fabric displacement (notmore than 7.74 sec; otherwise the transducer will bedamaged). If the picks/in is increased, the displacementof fabric will decrease. This point has been taken intoconsideration while determining the maximum sett. Aspicks/in increases, the displacement of fabric within afixed time (7 sec in the above example) decreases and astage is reached when the displacement of fabric isminimum and the indicator gives a constant reading.
Thus, for obtaining maximum weft sett for anygiven warp sett, picks/in was increased gradually atsuitable intervals. When the displacement of fabricfrom a fixed point within a fixed time became verysmall, after weaving 10-12 in fabric, actual picks/innear the fell of cloth was noted. This will be themaximum sett. It was also observed that at minimum
displacement of fabric in the transducer, the maximumfell-creep distance was 1.2cm. It was achieved whenthe maximum weft sett was obtained and the minimumlinear displacement occurred. The relationshipbetween the displacement of the fabric and picks/in isshown in Fig. I. It is observed that the relationship isparabolic in nature, obeying the equation Y = 89.1981.998 X +0.012 X2. The displacement of the fabric is
39
INDIAN J. TEXT. RES., VOL. 9, JUNE 1984
more fbr lesser picks/in, and it decreases as the picks/inis increased. It is also observed that at a certain
m~~i~um weft sett, the displacement of the fabric ismInImum.
Cloth setting-With a given warp tension and warpsett, there is a certain value of weft sett which will
enable weaving to proceed without any abnormaldifficulty in beating up the weft and without excessive
end b~eakages. When this sett is exceeded or thespacing decreased, difficulty arises in weft insertioninto the cloth by the reed and the consequential rise inpeak warp tension at beat-up. Closer sett or decreasedweft sp~cing causes increase in fell-creep distance. Thisis due to the fact that picks are not pressed sufficientlyclose in the fabric during beat-up. The cloth-fell will,therefo~e, move nearer to the reed an.d the cloth willbuckle at beat-up. The warp is, therefore, pulledforward as the cloth is bumped to the fully forwardposition of the reed. As the weaving proceeds, thecloth-fell position moves nearer to the reed when fellcreep distance reaches 1.2cm, at which weavingbecomes impossible on account of excessive warpbreaka~es and/or excessive buckling. Thus, forobtainihg maximum weft sett for any given warp sett,picks/in was increased gradually at suitable intervals.
The fellrcreep distance went on increasing as the picks/in was increased and at 1.2cm fell-creep distance,maximum weft sett was obtained, because after 1.2cmfell-credp distance it was impossible to weave thefabric.
The relationship between picks/in and fell-creepdistance is also shown in Fig. I. It is observed that aspicks/in increases, the fell-creep distance also increases
and the relationship between these two parameters isparabolic, obeying the equation Y = 1.44 XZ +5.17 X-124.87. It is also observed that the rate of increase infell-creep distance for a pick increase is higher withhigher weft sett.
Results and Discussion
The ends-picks relationship for three different weftcounts (2/20',2/40' and 2/60') for 2/2 right hand twill isshown in Fig. 2. The relationship is almost linear for allthe three weft counts. A similar trend is found for allother weaves, as is evident from Figs 3-7. Highermaximum weft sett is obtained for fabrics of equalfirmness with finer weft yarn and lower reed. Thereason for the former is that the finer weft yarn is morecompact and it is possible to insert more equivalentweft sett than in the case of coarser weft yarn for thesame weaving difficulty.
Comparison of experimentally obtained maximum
weft setts with those of Law's and Brierley's rules-It isvery difficult to make an accurate comparison ofexperimentally obtained weft setts with those obtainedby the rules of Law and Brierley, because the weavingconditions under which they conducted their workhave not been specified. Also, they did not specifywhether the theoretically calculated values correspondto loom state, dry-relaxed or wet-relaxed fabrics. Thegeneral rules for unbalanced setts in plain, matt andtwill sateens given by Law and Brierley have a numberof drawbacks, e.g. (i) different classes of weave shouldhave different ends-picks relationships, (ii) a differentends-picks relationship should apply according to theaverage float of weave, and (iii)ends-picks relationship
0---0 BRIERLEY0----0 EXPERIMENTALo-._.~ LAW
1407·5
EE
6'5~
\lOaCD Lt
I.LL
Ua
~f-
a::z ww
a..::;:
~w u '"<l:
u--J
a::
5'5 B;
600
2/2 RIGHT HAND TWILL
WARP COUNT-2/405WEFT COUNT-2/405
~\\\\
\
~
"'" 2Y= -124'1817+5'17467X +1·441 X
0,65
0,5
fu \
~ ~I /\f:! Q,~ 2 '
is VI =89'198 -1·99aX +0'012 X '0,a.. ,·5 '0wwa::
':' 1'2~uj 1'0LL 0,95
8880
ENDS PER INCH
72
Fig. 2-Relationship between warp sett and weft set! for 2/2 righthand twill
9060 70 80
PICKS PER INCH
Fig. I-Effect of picks/in on the displacement offabric (0--- 0--- 0)and fell-creep distance (0 - 0 - 0)
SHARMA et at.: SETTING LIMITS FOR TWILL WOVEN FABRICS
increase in weft count, the slope of the curve increases.Experimental weft setts are 3.22 and 11% lower thanBrierley's maximum setts and 26.87 and 8.32% lowerthan Law's maximum setts for 2/20s and 2/60s weftcounts respectively. A similar trend is observed in thecase of 4/4 right hand twill (Fig. 4), i.e. experimentalweft setts are lower than Brierley's and Law'smaximum weft setts for 2/40s and 2/60s weft counts,except a slight increase in experimental weft sett ascompared to Brierley's maximum sett. The slope of thecurve increases with increase in weft count.
It is clear from Fig. 5 that in the case of211/121 righthand twill, experimental weft setts are 38.72 and 10.9%higher than Brierley's maximum weft'setts for 2/20sand 2/40s weft counts respectively. While comparingwith Law's maximum weft sett, experimental weft settis 6.79% lower for 2/20s weft count and 5.66% higherfor 2/40s weft count. For 2/60s weft count,experimental weft sett is lower than Law's maximumweft sett for the coarser reed. For finer reed (88's),experimental weft sett is 1.57% lower than Brierley'sweft sett and 18.7% higher than Law's weft sett for2/(;OSwet count. The slope of ends-picks curveincreases with increase in weft count.
Fig. 3-Relationship between warp sett and weft sett for 3/3 righthand twill
0..-.---.-0.-----.-02/205 WEFT
~- --- __ 5Y=90'67=O:j75X 2/20 WEFT
should vary according to the square sett about whichthe comparison is made.
On the basis of square setts deduced in the presentwork, the unbalanced setts of Law and Brierley werecalculated(Table 1).The calculated setts along with theexperimental setts are plotted in Figs 2-7 for differentweaves (2/2, 3/3, 4/4, 211/121, 3/5 and 2/6). Themaximum weft setts obtained by Law's rule are veryhigh as compared to those obtained by Brierley's ruleas well as experimental weft setts for all the coarser andfiner counts. Brierley's theoretical weft setts werecompared with experimental weft setts.
The variations in Brierley's theoretical andexperimental maximum weft sett values are possiblydue to the different machine and weaving conditionsused. Snowden 8 also pointed out that the limits of settsare obtained according to the type of loom, i.e.whether it is of light or heavy construction, whether ithas positive or negative dobby, whether it has negativeor positive let-off and whether it has negative orpositive take-up. He also found that different limits ofsetts are obtained according to the conditions ofweaving, i.e. warp tension arranged, the timing of shed.change and the position of back rest (neutral or raised)tension for maximum effect. Fig. 2 shows the endspicks relationship for 2/2 right hand twilL It is foundthat in the case of 2/20s weft count, experimental weftsett is higher than Brierley's maximum sett and lowerthan Law's maximum weft sett. Experimental weft settwith 2/40s weft count is also higher than Brierley's weftsett. In the case of 2/60s weft count, experimental weftsett is lower than Brierley's maximum weft sett. Thismay be due to reduction in the compressibility of thefiner yarn. Therefore, in the case of 2/2 right hand twill,the slope of the curve increases with increase in thefineness of count.
In the case of 3/3 right hand twill (Fig. 3),experimental maximum weft setts are lower thanLaw's and Brierley's theoretical setts for all the threeweft counts, but the difference between experimentaland theoretical weft setts increases as the weft countincreases. It is also observed from Fig. 3 that with
Table I-Unbalanced Setts of Law and BrierleyWeave Law's square settBrierley's square sett
Fig. 5-Re1ationship between warp sett and weft sett for 211/121right hand twill
2{605 WEFT
0---0 BR IERLEY
0---0 EXPERIMENTAL
'\\''\
'~.
220
180
100
120
140
200
260
320~300
ffi 160Q.
V'l""Uc:
::cuz
Fig. 4-Relationship between warp sett and weft sett for 4/4 righthand twill
Ends-picks relationships for 2/6 and 3/5' twillstructutes are shown in Figs 6and 7. It is observed thatBrierley's weft setts are same for both the weaves forthe same average float length. The experimentalmaxim:um weft setts are also approximately the same,except for minor variation in the case of 2/6 twill. It isdue to the fact that maximum float length in 2/6 twill ismore than that in 3/5 twill. With 2/60s ahd 2/40s weftcounts experimental maximum weft setts are lowerthan Bfierley's maximum weft setts for both the twills.The values of experimental weft setts are 51.62 andI58.93~ lower than Law's maximum weft setts and 7.30
and 24,52% lower than Brierley's maximum weft settsfor 2/4ps and 2/60s weft counts respectively iIi the caseof 2/6 twills. For 3/5 twill, the values of experimentalweft setts are 44.16 and 53.38% lower than Law'smaximi\lm weft setts and 7.79 and 26.25% lower thanBrierley's maximum weft setts for 2/40s and 2/60s weftcountslrespectively. With 2/20s weft count, the value of
experirpental weft sett is 5% high~r than Brierley'smaxim~m weft sett in the case of 2/6 twill, but in the
80
6072
2{205 WEFTI T
80 88ENDS PER INCH
case of 3/5 twill, it is very close (1.56% higher) toBrierley's maximum weft sett and 38.89% lower thanLaw's maximum weft sett. It can be concluded thatLaw's weft setts are much higher than the experimentalweft setts, whereas Brierley's maximum weft setts areclose to experimental weft setts, irrespective of warpsett and weft count. The slope of the curve increaseswith increase in weft count in both the cases.
It is evident from Figs 2-7 that the slopes of endspicks curves increase with increase in weft count. It isalso observed that as the counts ratio (weft to warp)increases, the slope of ends-picks curve increases. Thisshows that the slope of ends-picks curve is directlyproportional to the counts ratio. This trend is observedin all twill structures, because as the counts ratiodecreases, the weft yarns become correspondinglycoarser, resulting in a lower rate of picks/in increaseper end decrease under a given warp tension. Therelationship between the weft to warp counts ratio (X)
and the slope of ends-picks curve (Y) isY =0.9555 y>.551362
It has also been observed that with the sett ratio(warp to weft) exceeding unity, it is possible to insertmore picks/in, whereas with the sett ratio less thanunity, it is not possible to obtain as many picks/in, assuggested by earlier workers5•6. With a given warpcount and different weft counts, the square setts withweft finer than warp are higher than those when the
42
SHARMA et at.: SETTING LIMITS FOR TWILL WOVEN FABRICS
5240 WEFT2605 WEFT
0---0 BRIERLEY
0------0 EXPERI MENTAL
0--,-,0 LAW
......
..•..•..
..•..•..
-q,\,
\,'\\ \
\
100
340
220
I180
u ~0:UJ"-(/)'"ua:
140
0----0 BRIERLEY
2/60SWEFT
~ 0----0 EXPERIMENTAL""
'~'T-0LAW
.~."'
.~'u2/60SWEFT280
430
220
400
340
140
120
200
I~ 1800:UJ"
V1
G 160ii:
ENDS PER INCH
Fig. 7-Relationship between warp sett and weft sett for 3/5 righthand twill
100
80
~'r-7J
.:: J.JJ--<I!:?sx
--()... - -- -- - -0 2/20sWEFT
, r
72 80 88
ENDS PER INCH
4072
2/205WEFT-L--88
Fig. 6-Relationship between warp sett and weft sett for 2/6 righthand twill
counts of warp and weft are reversed. The reason forthis is that with counts ratio more than unity, finerwefts (2/605) can be more easily beaten on the coarserwarps (2/405), giving higher weft setts.
Relationship between weave value and aver{lge float
length-Law's formula for calculating weave value is
W =I{1+ 5% more for each float length exceeding
two, where I is the average float length; and W, theweave value. Brierley's formula for weave value is W
=1m, where m is a constant and its value for twillstructure is 0.39.
The experimental weave value has been found usingthe relationship:
PPI X £0.67 x (a/b)1/2
(k x c)112
where 1m is the weave value; PPl, picks per inch;£, ends/in; a, warp count; b, weft count; c, averagecount of warp and weft, and k is a constant, its valuebeing 200 for cotton system. The relationship betweenweave value and average float length is shown in Figs8-10 for 72" 805 and 885 reeds respectively. It isobserved that Brierley's weave values are higher thanLaw's weave values. Experimental weave values havebeen found to be closer to Brierley's weave values, andthey increase with increase in the fineness of count forall the three reeds and for each float length.Experimental weave values for 2/405 warp count and2/205 weft count are higher than Brierley's weave valuesfor all the three reeds (72" 805 and 885) but for minorvariation in the trend for higher float length in the caseof 805 and 885 warp setts. For 805 warp sett,experimental weave value is lower than Brierley'sweave value for a float length of 4. But for 2/405 warpand weft count with lesser float length, experimentalweave value is higher than Brierley's weave value andwith longer float it becomes lower than Brierley's
43
INDIAN J. TEXT. RES., VOL. 9, JUNE 1984
0----0 EXPERIMENTAL
0----0 BRIERLEY
2/40SWEFT
2/60sWEFT
s2/20s WEFT
2/40 WEFT
wl><lw~
w::>-'<l>
0--0 EXPERIMENTAL
0----0 BRIERLEY
0'-'-<) ~AW
UJ::>-'~UJ
~w
~1
2 3 4AVERAGE FLOAT LENGTH
Fig. 8-Relationship between weave value and average float lengthfor 72' reed 2 3
AVERAGE FLOAT LENGTH
Fig. 10- Relationship between weave value and average float lengthfor 88' reed
Fig. II-Relationship between fell-creep distance and cover factorfor 88' reed and 2/2 right hand twill
2 3 4
AVERAGE FLOAT LENGTH
Fig. 9-Relationship between weave value and a'lerage float lengthfor 80' reed
weave value. In the case of 2/60s weft count,experimental weave values are lower than Brierley'sweave values for all the warp setts (72" 80S and 88S) andfloat lengths. It is observed from Figs 8-10 that as thecounts ratio (warp to weft) decreases, the weave valueincreases. For higher average float length, experimental weaye value is higher than Brierley's weave valuefor all the reeds. This finding is in close agreement withthose of Varma10. Because the experimental weavevalues for warp and weft interlacing twills agree withBrierley's weave values, it is obvious that Brierley'srule fot calculating the sett could apply.
Relationship between fell-creep distance and fabriccoverfactor-It is seen from Fig. 11 that with increasein weft sett, there is increase in fell-creep distance, asincrease in weft sett causes an increase in weft coverfactor as also the total fabric cover factor. Therelationship between fell-creep distance and fabriccover factor is found to be non-linear. This finding is inagreement with those of Greenwood 11,12 andSharma 13. A similar trend is observed for all the setts,weft setts, weft counts and all twill structures.
Conclusions
(1) The resistance encountered during weaving isrelated to fell-creep distance and warp sheet tension.
(2) Ends-picks relationships are linear for all theweaves.
(3) As the float length increases, experimental weft
44
SHARMA et al.: SETTING LIMITS FOR TWILL WOVEN FABRICS
setts become higher than Brierley's weft setts forcoarser counts.
(~ Brierley's formula for setting limits is moresuitable for coarser counts compared to finer counts.
(5) The maximum weft setts obtained by Law's ruleare very high compared to those obtained by Brierley'srule as well as experimental weft setts for all the coarserand finer counts.
(6) In the case of finer counts, the experimental weftsett is lower than Brierley's maximum weft sett due toreduction in the compressibility of finer yarn, while inthe case of coarser count, the results are in agreementwith those of Brierley.
(7) Deviation of experimental weft sett values fromBrierley's maximum weft setts decreases with decreasein the fineness of count.
(8) In the case of 211/121 twill, experimental weftsetts are higher than Brierley's weft setts but for minorvariation in trend for finer count.
(9) Experimental weave values are closer toBrierley's weave values for some reeds, whereas Law'sweave values are much lower for all reeds.
(10) Fabric cover factor is non-linearly related tofell-creep distance.
AcknowledgementThe authors are thankful to Prof. R.C.D. Kaushik,
Director, TIT, Bhiwani, for permission to publish thispaper and to Shri Sandeep Ranjan for preparing thesamples.
References
I Owen A E, J Text lnst, 19 (I 'J2li)"1'365.2 Peirce F T, J Text Inst, 28 (1937) T45.3 Ashenhurst T R, Text Educ, (1888-89) 335.4 Armitage E Huddersfield, Text Soc J, (1907-08).5 Law W, Wool Rec Text Wid, 21 (1922) 968.6 Brierley S, Text Mfr, 57 (1931)3;58(1932) 178,342;78(1952) 349,
431,449,595; 79 (1953) 71, 189,293.7 Chamberlain N H & Snowden D C, J Text Inst, 39 (1948) T23.8 Snowden D C, J Text Inst, 40(1949) T317; 41 (1950) T237, T832.9 Varma D S, Setting limits of corkscrew weaves, M.Sc. thesis,
University of Leeds, 1961.10 Varma D S, Proceedings, 10th technological conference of
ATIRA, BTRA and SITRA, 1968, 191.11 Greenwood K, Text Rec, 127 (1959) 66.12 Greenwood K & Cowhig W T, J Text Inst, 47(1956) T74, T241,
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13 Shll{ma I C, Bharga va G S & Agarwal S C, Indian J Text Res, 7(1982) 107.
