Page 364 - Anthropometry, Apparel Sizing and Design

356 Anthropometry, Apparel Sizing and Design

under elongation and methods of correction of the pattern blocks from loose shapes
into tight-fitting shapes.
Knitted materials have shrinkage (or edge curl). The amount of shrinkage is deter-
mined by the material type, structure, processing technology, and finishing methods.
Due to the laddering characteristic of the knitted materials, the seam allowance
(including sewing loss) is usually 0.12–2.50cm. In order to obtain the necessary
pressure on the shoulder area, the pattern block should be reduced by an average
of 10% compared to the dimension, calculated for a rigid cylinder of the same size
(Ng, 2001).
When knitted material has good draping and little shrinkage, the length and
width of the finished pressure garment will become longer and narrower. To get
a desirable shape, the pattern block should be drawn with negative ease in the
horizontal. When knitted material has poor draping and large shrinkage proper-
ties, we need to increase the length in the vertical in the pattern block. To sum
up, the pattern drawing rules should include edge size (seam allowance), sewing
loss, horizontal ease, vertical shrinkage and other various shrinkages, etc.
(Anbumani, 2007).
Due to the characteristics of the yarn coil structure, the shrinkage rate of most knit-
ted materials is from 2% to 7% (Zhang, 1990; Cui and Wu, 2018). Fig. 13.14 shows the
relationship between the elongation and the shrinkage of knitted materials used for
daily underwear, tight-fitting garments, shapewear, etc.) measured in two perpendic-
ular directions.
For example, the basic pattern block of a T-shirt is designed with bust girth 84cm
and an ease value of 6cm (total width is 84+6¼90cm) and the full length is 50cm. To
modify this basic block into a block for a tight-fitting T-shirt, and in order to prevent
the impact of tensile and shrinkage of the material after wearing, the horizontal size is
reduced (84 8¼76cm), but the amount of shrinkage is needed to be designed in
the longitudinal direction, that is, the length of the tight-fitting T-shirt becomes
50+3¼53cm.

Fig. 13.14 Relationships between the elongation and the shrinkage of knitted materials in warp
(A) and in weft (B).