ETS (Engineering Textile Structure) NOTES






Theory and calculation of cover factor


The figure shows projected views of two woven cloths of different construction. At A the warp and the weft threads cover the area of the cloth only partially, but at B the cloth area is covered completely with no spaces left between the adjacent warp yarns, and it will be seen that the relative closeness of yarns in a woven cloth is dependent upon the ratio of yarn diameter, d, to yarn spacing, p. This ratio known as relative cover, can be defined as the proportion of a projected view of a given area of cloth which is covered by threads, and will have a scale from 0 to 1, although it may also be expressed as percentage cover with a scale from 0 to 100 per cent.

d/p = relative cover,
(d x 100)/p = percentage cover

It is preferable to express warp and weft relative cover separately, as the cumulative value of cloth cover does not indicate the comparative importance of each set of yarns which is essential for the determination of certain cloth characteristics.

From the relationship shown above it will be obvious that if d= p. the value of relative cover is one, and this is regarded as the theoretical maximum cover. In practice, however, this value can be exceeded  considerably in any one direction, either through yarn distortion, or, by forcing the threads into different planes, especially if the relative cover of the opposite set of threads is reduced correspondingly.
The relative cover for one thread system can be calculated as follows by considering an area of 100 x 100mm:

Area per thread = 100 x d
Area covered by n threads of one system = n x 100 x d
Therefore, relative cover = (n x 100 x d)/(100 x 100) = (n x d)/100

Example: The cloth represented at A is specified as follows: Warp — 25 tex cotton, 267 ends/100 mm; weft—36 tex cotton, 334 picks/100 mm. Find the relative warp and weft cover. (Subscript 1 refers to warp, subscript 2 to weft.)

Warp relative cover = (n1 x d1)/100
= (267 x (25)/(26.7))/100
= 0.50

Weft relative cover = (n2 x d2)/100
= (334 x (36)/(26.7))/100
= 0.75

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Effect of Weft parameters on Weaving Performance and Fabric Properties


Threads per inch and yarn count are some of the most important parameters that affect both weaving performance and fabric property.Experimental studies were conducted by weaving fabrics with three different picks per inch (PPI)and weft counts. The study shows that weaving performance is affected by the too high cover factor. Cover factor was calculated by dividing the threads/inch by the square root of the English cotton count and end breakage was taken as an indication of weaving performance. It was observed that when the count as well as threads/inch of one series of yarn changes the crimp% i.e. the consumption of both series of yarns are affected. It was also observed that, as expected, when the threads/inch increases the fabric strength also increases but at higher threads/inch the gain in strength is relatively more.

Keywords: Threads, cover factor, EPI, PPI,crimp, strength, weaving performance.

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Feature based 3D garment design through 2D sketches

Charlie C.L.Wang* Yu Wang Matthew M.F.Yuen
Department of Mechanical Engineering, Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong


This paper presents a new approach for intuitively modelling a 3D garment around a 3D human model by 2D
sketches input. Our approach is feature based – every human model has pre-defined features, and the
constructed garments are related to the features on human models. Firstly, a feature template for creating a
customized 3D garment is defined according to the features on a human model; secondly, the profiles of the 3D
garment are specified through 2D sketches; finally, a smooth mesh surface interpolating the specified profiles is
constructed by a modified variational subdivision scheme. The result mesh surface can be cut and flattened into
2D patterns to be manufactured. Our approach provides a 3D design tool to create garment patterns directly in
the 3D space through 2D strokes, which is a characteristic not available in other computer aided garment design
systems. The constructed garment patterns are related to the features on a human model, so the patterns can be
regenerated automatically when creating the same style of garment for other human models. Our technique can
greatly improve the efficiency and the quality of pattern making in the garment industry.

Keywords: sketched input, 2D strokes, 3D design, computer-aided design, garment industry

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