Knitting Science 2, Production Calculation

Knitting Science (2)
Jimmy Lam
Institute of Textiles & Clothing
Learning Objectives
Tightness factor and fabric properties
 Maximum cover factor
 Application of fabric geometry
Tightness factor and fabric
Physical properties of the fabric that related to
cover factor or tightness factor:
transparency and air permeability;
shrinkage of a fabric
pilling and snagging effect
flexural rigidity and extension
tightly or slackly of fabric
Transparency and air permeability
Since the value of tightness factor can show the
openness of the fabric, ie the higher the tightness
factor, the lower the openness of the fabric
 Also the openness of the fabric is directly related
to transparency and air permeability.
 Therefore, the higher the value of tightness factor,
the lower of the transparency and air permeability
character or vice versa.
Shrinkage of fabric
If the same type of yarn is
used, the tighter the fabric
(or higher the tightness
factor), the lower the
shrinkage of the fabric.
 It is because the tightly
knitted fabrics simply
cannot shrink as much as
before adjacent loops jam
against each other.
Pilling an snagging effect
Since the tightly knitted fabric,
the movement of fabric or yarn
is more difficult than snack
fabric, therefore the pilling or
snagging is more difficult to
occur in the tightly knitted
 It is because the effect of pilling
and snagging is determined by
the movement of fiber or yarn.
Flexural rigidity and extension
The higher the tightness factor of the fabric
shows the higher the flexural rigidity and lower
the extension properties of the fabric
Tightly or slackly fabric
They are related to the handle of the fabric.
 As said previously, the higher the tightness
factor, the tighter the fabric or vice versa.
 Also if the fabric is tightly knitted, the hand
feels of the fabric is not so soft.
 However, a tightly knitted fabric gives a better
fabric dimensional stability.
Maximum Cover Factor
Maximum Cover
For a maximum cover, an equilateral
triangle is constructed.
 CD2 = BC2 - BD2 = 1-(1/2)2
 CD=Sqrt(3/4) = 0.866
 Since AB is wale width and CD is
course depth;
 the max cover is
– wale width : course depth = 1: 0.866
Max Cover (2)
As wales per unit length and courses per unit
length are equal to the reciprocals of wales
width and course depth, therefore
 wales/unit length : courses/unit length = 0.866:1
 That is, 86 wales to 100 courses in the plain
fabric is the condition to have maximum cover
in a plain knitted fabric
Application of fabric geometry
Fabric weight per unit area
Fabric weight per unit area (g/m2)
– let S is stitches per cm2;
– l is loop length in mm; and
– T is yarn count in Tex
No. of stitches in 1 m2 = S x104;
 Fabric weight = S x 104 X l/1000 X T/1000
– As S=Ks/l2;
– g/m2= Ks/l2 X 104 X l/1000 X T/1000
g/m2=Ks T/(100l)
Fabric weight per running meter
Running meter is one meter length of fabric measured
along the direction of production irrespective of width.
Number of courses in one meter = cpcm X 100
If n is no. of needles, total stitches = n X cpcm X 100
g/m = n X cpcm X 100 X l/1000 X T/1000
– Since cpcm= Kc/l
– g/m = n X Kc/l X 100 X l/1000 X T/1000
g/m = nKcT/10000
Fabric Width
Width = number of needles in knitting / W = n/ W
 where W is wales per unit width (wpcm)
 Since W=Kw/l
 Width = nl/Kw
Fabric length
Fabric length = number of feeders X rpm /C
– where C is course per unit length
Since C=Kc/l
 fabric length = Feeder X rpm X time taken (min)
X l / Kc

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