Presentation on theme: "Chapter Four: Combined Weaves Concept: Combined weaves are constructed on the basis of two or more fundamental weaves and their derivatives. The combined."— Presentation transcript:
Chapter Four: Combined Weaves Concept: Combined weaves are constructed on the basis of two or more fundamental weaves and their derivatives. The combined weaves produce irregular or uneven fabric surface or small woven figures on the fabric. Combined weaves may be divided into the following groups: Stripe and check weaves Crepe weaves Mock leno weaves Huckaback Honeycomb weaves Bedford weaves Distorted weaves
4.1 Stripe and check weaves Stripe and check weaves are made with longitudinal and cross stripes of different widths and different weaves on the surface. The main point of this weave making is to calculate the weave repeats.
A fabric sample:
1.Calculation and Construction of Stripe Weaves Calculation and construction of fabric with longitudinal stripes: In this case, the warp repeat depends on: 1) number of stripes; 2) the width of each stripe; 3) the warp density; and 4) the stripe weave. See the figure next page:
As we can see here, this fabric contains 3 stripes and the width of the stripes are A,B (cm), then the warp repeat of the fabric is: Ro=P O A+P O B= P O (A+B) Where: P O is the warp density per cm.
The weft repeat equals the LCM (least common multiple ) of the weft repeat of the stripe weaves. Notes: To calculate the number of warp threads, the warp density is multiplied by the width of each stripe. The numbers obtained must be corrected to get a whole number of the repeats in each stripe.
2. Cross stripes weaves The number of threads in the weft repeat depends on the number of stripes, width of each stripe, weft density, and stripe weaves. See the figure below:
R y = The warp repeat (R O ) equals the LCM of the warp repeats of stripe weaves. Similar to longitudinal stripes, the repeats can be achieved in the same way:
3. Calculation of Fabrics with Checks from Different Weaves Example for handkerchief fabric. Fig.4.3:
a = 7.5 cm d = 3.0 cm g = 1.5 cm b = 1.5 cm e = 24 cm h = 1.5 cm c = 1.5 cm f = 7.5 cm i = 3.0 cm j = 24 cm P O = 21.4 th./cm P y = 19.5 th./cm (th./cm means threads per cm) The following characteristics are given: The weave of the background is plain and of the border, a 4-shaft sateen.
From Fig. 4.3 we know stripe has the structure of a fabric with cross stripes. The warp repeat of this stripe equals LCM of the warp repeats of the plain and sateen weaves (R=4). The number of threads in the stripe equals the warp density multiplied by the stripe width, i.e. P oa = 21.4×7.5 = Let’s correct this number to 160; 160/4 = 40, so 40 elementary repeats can be placed within the stripe a. Stripe a:
The elementary warp repeat in this stripe is 4. The number of threads P Ob = 21.4×1.5 = This number is corrected up to 32. For 32÷4=8, so the elementary repeat can be placed within the stripe 8 times. Same way can be used to calculate the others stripe, and then sum of them. Stripe b:
Home works: Calculate the repeats of the fabric according to the given pattern below. Background weave is plain, and the border weave 1/3 broken twill. a = 7cm b = 2.1cm c = 20cm d = 7cm e = 2.1cm f = 20cm P O =23 th./cm P y =20 th./cm
4.2 Crepe Weaves Concept: Crepe fabrics are characterized by a pebbly or crinkled surface. Methods of getting crepe effect 1) The crepe effect can be achieved by using crepe yarns 2) The crepe effect can be achieved by using crepe weaves 3) The crepe effect can be achieved by using some special fishing processes.
Construction of crepe weaves 1 Drawing one weave over the other 2 Arranging the warp overlaps in sateen order 3 Rearranging warp 4 Rearranging warp and weft 5 Placing the warp threads of one weave among the threads of the another weave 6 Placing the warp threads of one weave among the threads of its reverse. 7 By the method of rotation 8 Saving shaft method
1. Drawing one weave over the other.
Main points: 1) Choose at least two weaves, and one of the weaves is very often sateen. 2) The type of shedding motion of the loom should be taken into consideration. It is common to choose those with the same repeat.
Some explanation: In the example shown in Fig. 4.4,the repeat of the sateen at A is equal to the repeat of the twill weave at B, so the weave crepe weave constructed at C has the same repeats, else, the repeats is found as the LCM of the former two base weaves. The constructed weave at C is characterized by non- uniform arrangement of the shaded squares. The shaded squares are concentrated on the warp threads 2 and 5 and weft threads 4 and 5. As a result the arrangement of warp overlaps becomes irregular. The fabric with such a weave has a pebbly surface.
2. Arranging the warp overlaps in sateen order. → ＝ This crepe weave is constructed on the base weave of sateen, and two shaded squares are added above and at right of each of the seven shaded squares, then the crepe weave is obtained in Fig.4.5. Actually, it is a reinforced sateen. Original weaveAdding warp overlapsFig.4.5 final crepe weave
3. Rearranging warp. The warp overlaps on the crepe weave at A are concentrated in four groups, making the surface of the fabric irregular and creating the pebble effect. Fig. 4.6
4. Rearranging warp and weft Fig.4.7 weaving plan of crepe weave
The lifting plan at A is constructed according to the base weave. The draft at B is constructed on the number of shafts equals the weft repeat of the base weave. The draft determines the arrangement of warp threads in the weave at C. Fig.4.7 at C is a crepe weave, and the Fig.4.7 at F is another crepe weave.
5. Placing the warp threads of one weaves among the threads of the other weave. Here we can see in Fig.4.8, the ends at B in red are placed among that of A in black, so crepe weave at C is produced. Notes: More often the ratios of the basic weave repeats are 1:1, otherwise, the repeats of the crepe weave are the LCM of P yA & P yB and P OA &P OB C Fig. 4.8
6. Placing the warp threads of one weave among the threads of its reverse. Fig. 4.9 To get the crepe weave at C, all the even threads of the first weave are replaced by that of the reversed weave. A B C
7. By the method of rotation Fig Construction of crepe by method of rotation Details can be found next page
In Fig at A the base weave is shown. This weave is turned through 90 0 in a certain direction, for instance, clockwise as at B. The weave at B is next turned one quarter way round to get the weave at C. Another quarter turn gives the weave shown at D. Then all these weaves are transferred to the same drawing at E to make a crepe weave. Method of rotation
8. Saving shaft method This method can produce a very big repeat to avoid any regular patterns on the surface of the fabric. Fig.4.11
The steps of construction 1) Determine the shafts, see Fig. 4.11, 6 shafts are selected. 2) Design the repeat. The warp repeat R o should be divided by the shaft selected and the weft repeat should be close to the warp repeat. Here; R O =6×10=60. R y =40 3) Determine the movement of each shaft. We need pay attention about: The floats of each end should be less than 3 The number of the intersection in each end should be close The warp floats should be close to weft float of each ends
4) Draft plan Sometimes we need work for several times until the fabric’s appearance meets the requirement we need.
Home works: 1. Constructing a crepe be rearranging warp the base weave is ↗, the sequence of the warp threads are 1, 3, 6, 2, 5, 4, 7, constructing a crepe by the method of rotation with the base weave at right, and each weave turns 90°in counterclockwise direction. 3. What are the advantages of the saving shaft method to produce crepe weave?