Standardization of Knitting Scheme Mr. Arkin Ng, Dr Jimmy Lam, Ms White Pak Institute of Textiles & Clothing The Hong Kong Polytechnic University

The 9th Asian Textile Conference, June 28-30, Outlines Introduction and Background Experimental Details Results and Discussions –Fabric dimensions and tightness –Fabric thickness and fibers –Fabric dimensions and fibers –Fabric extensibility and fibers Conclusions

The 9th Asian Textile Conference, June 28-30, Introduction & Backgrounds Flat knitting is one of the most important technological inventions for knitwear design and production that has gone through a lot of changes over time. When comparing the primary flat knitting using jacquard steel for needle selection with the state-of-the-art machine for integral shape knitwear, one can readily realize the amount of breakthroughs in this procession. The huge improvement in the efficiency of loop transfer has replaced the flat bed purl knitting machine with double hook latch needles.

The 9th Asian Textile Conference, June 28-30, Introduction & Backgrounds The knitting production process evolved from cut-and-sewn piece goods knitting to fully fashion shaped knitting, and finally to integral shape knitting. The latest machine has completely eliminated the cutting and linking processes and put things together in one single operation.

The 9th Asian Textile Conference, June 28-30, Stage One: Cut and Sewn Stage Two: Shaping Stage Three: Integral Knitting Stage Four: Whole Garment Knitting Evolution of Knitwear Technology

The 9th Asian Textile Conference, June 28-30, Introduction & Backgrounds 2 Despite all these technological developments in flat knitting, the key instructional method (knitting scheme) is still relied on the skill and experience of individual knitting technician. With increasing demand for fine gauge knitting and 3-D products, ability to produce fine and accurate knitting schemes is critical for quality assurance and production. Conventional knitting schemes are work of individual often lacking in consistency amongst their compliers. This trial-and-error approach which is sufficient for coarse gauge loose body knitting but crude on body-fitted knitting.

The 9th Asian Textile Conference, June 28-30, What is Knitting Scheme ? Knitting scheme is the statement used to knit the garment parts which is expressed in terms of courses (fabric length), needles width (fabric width) and fashioning frequencies. A swatch (a small piece of fabric) in correct knitting instruction and knitting tension is normally prepared before bulk production. One of the useful methods to determine the stitch tension is to stretch the fabric lengthwise to its utmost limits manually and measure the dimension of 10 wales board.

The 9th Asian Textile Conference, June 28-30, What is Knitting Scheme2 ? The number of wales and courses per cm after finishing which is determined from the swatch to prepare the knitting scheme. The swatch is set and the knitting scheme is written according to the stitch density and the style of knitwear. Typical knitting scheme is shown in Figure 1

The 9th Asian Textile Conference, June 28-30, Figure 1 Typical Knitting Scheme on Fully Fashion Panel

The 9th Asian Textile Conference, June 28-30, Effective Knitting Scheme An effective knitting scheme should embrace good knowledge of: 1.Knitting structures; 2.Knitting machine and functions; 3.Shaped panel design; 4.Assembling and finishing; 5.Knitting scheme calculation and 6.Costing

The 9th Asian Textile Conference, June 28-30, Experimental Details A hand knit flat bed machine with 36 inches width, 12 gauge and 432 needles will be used to produce a jersey plain knitted fully fashion panel. A typical knitting scheme is shown in Figure 1 & 2.

The 9th Asian Textile Conference, June 28-30, Figure 1 Typical Knitting Scheme on Fully Fashion Panel

The 9th Asian Textile Conference, June 28-30, Figure 2 Knitting Scheme on Assembling of Fully Fashion Panel

The 9th Asian Textile Conference, June 28-30, Knitting Scheme shows the style of the knitwear & logo

The 9th Asian Textile Conference, June 28-30, Experimental Details 2 The fabric samples were knitted into three different tightness as suggested from the industry as shown in Table 1 Fabric DensityTightness (measured in 10 wales under tension) Tightness (measured in 10 wales under tension) Tight1-3/8”3.49 cm Normal1-4/8”3.81 cm Loose1-5/8”4.12 cm Table 1 Fabric density and tightness.

The 9th Asian Textile Conference, June 28-30, Experimental Details 3 Five different materials (wool, cashmere, Pima cotton, combed cotton and acrylic) with three different fabric tightness, total of 15 samples were produced. Fabric dimensions (fabric length, width and thickness) were measured both before and after washing under standard conditions.

The 9th Asian Textile Conference, June 28-30, Loop length under different tension from Knitting Scheme Measured 10 walesLoop length Materialunder tension (inch)(mm) Cotton Prima1 3/85.86 Cotton Prima1 1/25.92 Cotton Prima1 5/86.42 Cashmere1 3/85.82 Cashmere1 1/26.10 Cashmere1 5/86.20 Acrylic1 3/85.62 Acrylic1 1/25.98 Acrylic1 5/86.10

Results and Discussions

The 9th Asian Textile Conference, June 28-30, Fabric Dimensions and tightness Figures 3 & 4 showed the fabric dimensions under different tensions. The average courses/cm and wales/cm for denser fabric are 9.12 and 6.12 respectively The average courses/cm and wales/cm for normal fabric are 8.67 and 5.95 respectively. Results show that using the same knitting scheme, different fabric tightness will affect the final fabric dimensions.

The 9th Asian Textile Conference, June 28-30, Fabric Dimensions and fabric thickness Figure 3 Fabric density measured in 1-3/8” on acrylic fibre

The 9th Asian Textile Conference, June 28-30, Fabric Dimensions and fabric thickness Figure 4 Fabric density measured in 1-4/8” on acrylic fibre

The 9th Asian Textile Conference, June 28-30, Length (cm)Loop length MaterialTension Per 50 needles(mm)Yarn TexTightness Factor Cotton Prima1 3/ Cotton Prima1 1/ Cotton Prima1 5/ Cashmere1 3/ Cashmere1 1/ Cashmere1 5/ Acrylic1 3/ Acrylic1 1/ Acrylic1 5/ Calculated Tightness Factor under different knitting tension for the same knitting scheme

The 9th Asian Textile Conference, June 28-30, Different knitting tension and the tightness factor

The 9th Asian Textile Conference, June 28-30, Different loop length and tension for the same knitting scheme

The 9th Asian Textile Conference, June 28-30, Courses/wales per cm under different fabric tension before washing

The 9th Asian Textile Conference, June 28-30, Courses/wales per cm under different knitting tension before and after washing

The 9th Asian Textile Conference, June 28-30, Fabric thickness & fibers Under the same knitting scheme, it was found that fabric with different materials will have different thickness (Fig 5). Both cashmere and wool fibers show thicker fabric than cotton (combed and pima cotton) and acrylic fibers. The effect of washing would increase fabric thickness and therefore, all fabrics with different fibres content after washing show thicker fabric than unwashed fabrics. Construction of knitting scheme in term of fabric thickness must consider the effect of washing and fiber composition.

The 9th Asian Textile Conference, June 28-30, Fabric thickness & fibers Figure 5 Fabric thickness and textile fibers under the same knitting scheme

The 9th Asian Textile Conference, June 28-30, Fabric dimensions and fibers Figure 6 shows fabric dimensions for different materials before and after washing using the same knitting scheme. It can be seen wale width (before washing) of cashmere and acrylic is higher than pima and combed cotton. The effect of washing will reduce the wale width for all fibres. This can be explained by shrinkage of fabric which will increase the fabric thickness but reduce the wale width of knitted fabric.

The 9th Asian Textile Conference, June 28-30, Fabric dimensions and fibers Figure 6 Fabric dimensions and fibers under the same knitting scheme

The 9th Asian Textile Conference, June 28-30, Fabric extensibility and fibres Under the same knitting scheme, different fabric extension is measured under different loading, namely 20N, 10N and 5N force respectively (Fig 7). Under the loading of 5N force, the extensibility of wool, cashmere and cotton are similar except for acrylic fiber, which is the lowest one. When the loading is increased from 5N to 10N and 20N respectively, the extensibility of wool and cashmere fibres are highest. This can be explained by the crimp and helix nature of wool and cashmere fibres. They allow a higher fiber extensibility under higher tension.

The 9th Asian Textile Conference, June 28-30, Fabric extensibility and fibers Figure 7 Fabric extensibility and fibres under the same knitting scheme

The 9th Asian Textile Conference, June 28-30, Conclusions This paper shows the results of commercial knitting scheme on different fibres (wool/acrylic/cotton/cashmere) under three different knitting tensions (tight/normal/loose). Results show that different materials will affect the final fabric dimension in terms of fabric thickness, width and length. The construction of knitting scheme, must take into account the effect of fibres, knitting tension and washing on final fabric dimensions.

The 9th Asian Textile Conference, June 28-30, Acknowledgements The authors like to thank for the Natalia Fahsion Ltd to provide the data for experiment and the support from the University in term of Teaching Company Scheme for this project.