FABRIC CALCULATION

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FABRIC CALCULATION

• Calculations on weft consumption
• Calculations on warp preparation
• Calculations on warp/weft crimp percentage
• Calculations on fabric weight (g/m2)

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Weft consumption of a loomQuestion

• A loom runs at 210 picks/min at an overall
  efficiency 82. The warp width in the reed is
  1.2m and the linear density of the weft is 30
  tex. What is the weft consumption per 8 hours

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AnswerWeft consumption

• A) Length of weft used per hour at 100
  efficiency
• 1.2 X 210 X 60 /1000km 15.12km per hour
• B) At 82 efficiency, the length used in 8 hours
• 15.12 X 0.82 X 8 99.19km
• C) Weft consumption, for 30 tex yarn is
• 30 X 99.19 /1000kg 29.76 kg per 8 hours

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Warp PreparationQuestion

• An order for 220 pieces of woven fabric, each
  110m in length and 1.2m in wide, is received. In
  the finished fabric, the warp crimp is 9 and
  there are 38 ends/cm. The creel of the direct
  warping process has a maximum capacity of 500
  cones.
• A) How many back beams are required
• B) What length of warp is on each?

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Warp PreparationAnswer

• A) Total number of ends
• Ends/cm x finished width in cm
• 38 x 120 4560 ends
• Since the creel can hold 500 cones, the number of
  ends per back beam could be 456, and 10 back
  beams should be used
• B) The total length of warp is given by
• Number of pieces X piece length X (100crimp)/100
• 220X110X109/100 26,378m

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Crimp Percentage of Woven Fabric

• The crimp percentage is the difference between
  straightened thread length and the distance
  between the ends of the thread in the fabric.
• Crimp (l-s)/s x 100
• Measuring crimp practically is not always a
  simple procedure. The length of the crimped yarn
  may be easily measured, but to decide when the
  crimped yarn removed no longer retains crimp is
  not easy.

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Example Crimp

• Crimp , (Formula 1)
• C(L-S)/S 100
• Where L is warp length, S is cloth length
• Warp Length (L), (Formula 2)
• L(1C) S
• Where C is crimp , S is cloth length
• Cloth length (S), (Formula 3)
• SL/(1C)
• Where L is warp length, C is crimp

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Question 1Crimp

• A cotton cloth is analysed, and from a tested
  strip of 20cm, the mean warp length is 21.2cm.
  Determine both the crimp and take-up percentage.

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Answer

• Crimp Percentage
• (21.2 20.0) / 20 6.0
• Take up Percentage
• (21.2-20.0)/21.2 5.66
• N.B In many fabrics, there is not too great
  difference between the warp and weft crimps, but
  there are examples of quite large differences.
  E.g. in cotton poplin, the warp cirmp could be
  14 and the weft crimp in only 2

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Example 2Crimp

• Ex2
• Calculate the length of warp required to weave
  160m of cloth if the warp crimp is 12
• Ex3
• What length of cloth can be woven from 800m of
  warp if the warp crimp is 8

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Answer

• Ex2
• S cloth length 160m
• Crimp c 0.12 and therefore warp length will
  be
• C (l-s)/s X100 and c l/s -1 and l(1c)s
• L(10.12)160 179.2m

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Answer

• Ex3
• Warp Length, L 800m , find cloth length, s
• SL/(1c) 800/(1.08)
• 740.8m

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Fabric Weight Calculations(Areal Density)

• In the imperial system, fabric weight is
  expressed in ounces per square yard.
• In SI, the mass per unit area is grams per square
  meter.
• If we get a 10 cm x 10 cm fabric, the fabric is
  easy to measure and multiplied by 100 to give
  fabric weight (g/m2).
• However, if we dont have the fabric, the fabric
  weight can be calculated by fabric density
  (sett), yarn count and crimp percentage.

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Fabric WeightCalculation

• Question 1
• A cotton fabric is woven from 18 tex warp and 21
  tex weft. The fabric has 28 ends/cm and 25
  picks/cm, and the warp and weft crimp percentages
  are 2.5 and 9.0 respectively. Estimate the areal
  density (fabric weight g/m2)

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Answer

• Mass of warp per square meter
• (ends/m)/1000 x (100crimp)/100 x tex
• (28 x 100)/1000 x (102.5 18)/100
• 51.5 g
• Note factor 1000 is introduced because tex is
  defined in terms of g/km
• Mass of weft per square meter
• (picks/m)/1000 x (100crimp)/100 x tex
• (25100)/1000 x (10921)/100
• 57.2g
• Fabric weight 51.5 57.2 108.8 g/m2

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• If we use ends/cm in the formula, we could omit
  the factor of 100 on the bottom line, the total
  mass per square meter will be written
• (ends/cm x 100crimp x tex) (picks/cm x
  100crimp x tex) /1000
• (28102.518) (2510921)/1000
• 51.657.2 108.8g/m2

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Fabric WeightCalculation

• Question 2
• A satin strip cotton fabric is woven from a warp
  of 25 tex in the plain sections and from one of
  12 tex in the satin weave. There are 40 repeats
  of the pattern in a fabric width of 1.28m, each
  repeat being made up of 48 ends of plain weave
  and 72 ends of satin weave.
• The crimp is 8 in the plain weave and 5 in the
  satin weave. The weft is 14 tex, with 28 picks/cm
  and has 6 crimp.
• Calculate the aerial density of this fabric (g/m2)

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Answer

• For this patterned fabric in which varied yarns
  are used, each type of yarn will require separate
  treatment.
• Number of pattern repeats per meter width
  40x1/1.28 31.25
• Fabric Weight (Warp Yarn)
• Hence, number of plain weave ends/m 31.25 x 48
  and
• Mass of plain weave ends/m
• (31.2548)/1000 (10825)/100 40.5g
• Similarly, mass of satin weave ends/m
• (31.2572)/1000 (10512)/10028.4 g

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• Fabric Weight (Weft yarn)
• Mass of weft per meter
• 2810614100/1000 41.6 g
• Fabric weight (warp weft) per square meter
• 40.528.441.6110.5 g/m2

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Fabric Weight(Imperial System)

• Sometimes, we need to express fabric weight in
  Imperial System (oz/yd2), the calculation is as
  follows
• Question 3
• Calculate the fabric weight (oz/yd2) for the
  following cotton cloth
• 22s x18s, 64 x 60 and 6.5 x 8.5

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• Convert the system to SI
• Tex 590.5/cotton count
• Warp 590.5/22 26.8 tex
• Weft590.5/1832.8 tex
• Sett /cm Ends per inch /2.54
• Ends/cm 64/2.5425.2
• Picks/cm 60/2.54 23.6

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• Fabric Weigth (g/m2)
• (25.2106.526.8)(23.6108.532.8)/1000
• 155.g/m2
• Since 1 g/m2 0.029 oz/yd2
• Fabric Weight (oz/yd2) 1550.029
• 4.52 oz/yd2

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Fabric WeightDenier

• Question 4
• Calculate the weight of the fabric (oz/lb2) for
  the following nylon fabrics
• 45 denier x 45 denier 104 x 96 and 4 x 5

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• Convert it to SI
• Tex Denier /9
• Warp tex 45/9 5
• Weft tex 45/95
• Ends/cm ends per inch /2.54
• Ends/cm 104/2.5440.9
• Picks/cm 96/2.5437.7

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• Fabric Weight (g/m2)
• (40.9 x 104 x 5) (37.7 x 105 x 5)/1000
• 41 g/m2
• Since g/m2 0.029 oz/lb2
• Fabric Weight (oz/lb2) 41 x 0.029
• 1.19 oz/lb2