Transcript Document

3.2.3 Elongated twills
1) The density ratio changes the
fabric appearance. (See Fig.3.14)
See Fig.3.14





Tan α= / = Po/Py
The inclination angle depends on the
density ratio:
Po = Py; tan α= 1; α=450
Po＜Py; tan α＜ 1; α< 450
Po＞Py; tan α＞ 1; α> 450
1
py
1
po
2) The shift changes the fabric
appearance. (See Fig.3.15, Fig.3.17)
3) weave drawn:
(1) Calculate the repeats, RO & Ry
Ry=RyB
Where, ROB, RyB are basic twill repeats.
(2) Draw the first end according to the formula of the basic twill
(3) Draw the other ends according to the same formula, but with the
changed shift
4) Applications and sample

Some fabrics made from the diagonal
weave are: whipcord, lady’s cloth.
3.2.4 Curved twills
1) Concept


Curved twills produce a curvilinear appearance
when the inclination angle of diagonal increases
gradually.
As we know, the inclination angle of the diagonal
may be changed by changing the shift. The curved
twill can be constructed by alternating shift of the
basic twill in either vertical or horizontal direction.
The alternation of shifts is made by the wish of the
designer.
2) two points in designing:


The sum of shifts must equal 0 or can be
divided by a repeat without remainder.
The biggest shift must be less than the
biggest overlaps, for avoiding the curved
line breaking.
Example 1:
4 1 1
3 1 3

The basic twill is twill :

The curved twill with the
alternating vertical shifts
having the following
succession: So=2、2、2、
1、1、1、1、0、1、0、
0、1、0、0、0、1、0、
0、1、0、1、1、1、1、
2、2、2、2
 (Where the sum of shifts equals 26, two times of 13 which is the weave repeat )
Example 2:


The basic twill is still
4 1 1
twill: 3 1 3
The alternating vertical
shifts are 2、2、1、1、0、
1、0、0、1、1、0、1、
1、1、-1、–1、–1、0、
-1、-1、0、0、-1、0、1、-1、-2、-2.
3) Weave drawn
Drawing vertically curved twill weaves are as
following:
1) Calculating the repeats:
Ro = numbers of the alternating shifts.
Ry = weft repeat of basic twill
2) Drawing the first end according to the formula of the
basic weave.
3) Drawing the other ends based on the shifts designed.

Horizontally cured twill weaves can be drawn in a similarly way
4) Applications

Curved twill weaves are widely used for
decorative fabrics and apparel fabrics.
Home works:
1. Whipcords made from weave formula
(1) 71 12 11 11 12 1 1 So=2
5 1 1
(2) 1 2 1 So=2
drawing the above weaves.
 2. Drawing the curved weave, the basic
4 1 1
twill is 3 1 3 , the vertical shift S0=2, 2, 1, 1,
0, 1, 0, 0, 1, 1, 0, 1, 1, 1, -1, -1, -1, 0, -1, -1,
0, 0, -1, 0, -1, -1, -2, -2 ,and drawing the
weaving plan using as small number of
shafts as possible.
