Knitting Scheme Development from Art to Science Mr. Arkin Ng 1, Dr Jimmy K C Lam 2 1 Natalia Fashion Ltd, Hong Kong 2 Institute of Textiles & Clothing, The Hong Kong Polytechnic University

The 86th TIWC, Nov 18-21, 2008, Hong Kong 2 Outlines Introduction and Background Experimental Details Results and Discussions –Fabric dimensions and tightness –Fabric dimensions and machine gauge –Fabric dimensions and tightness factor –Fabric pilling and textile materials Conclusions

The 86th TIWC, Nov 18-21, 2008, Hong Kong 3 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.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.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 huge improvement in the efficiency of loop transfer has replaced the flat bed purl knitting machine with double hook latch needles.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 4 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 86th TIWC, Nov 18-21, 2008, Hong Kong 5 Stage One: Cut and Sewn Stage Two: Shaping Stage Three: Integral Knitting Stage Four: Whole Garment Knitting Evolution of Knitwear Technology

The 86th TIWC, Nov 18-21, 2008, Hong Kong 6 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 86th TIWC, Nov 18-21, 2008, Hong Kong 7 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 widthwise to its utmost limits manually and measure the dimension of 10 wales board.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 8 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 86th TIWC, Nov 18-21, 2008, Hong Kong 9 Figure 1 Typical Knitting Scheme on Fully Fashion Panel

The 86th TIWC, Nov 18-21, 2008, Hong Kong 10 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. Five different materials and three different knitting tensions and three different machine gauges were used, total of 45 samples were produced. The fabric samples were knitted into three different tightness as suggested from the industry and shown in Table 1.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 11 Table 1 Fabric density and tightness. Machine Gauge Knitting TensionTightness (measured in 10 wales) Tightness (measured in 10 wales) 5GTight3-4/8”8.09 cm 5GNormal3-7/8”9.84 cm 5GLoose4-2/8”10.79cm 7GTight2-4/8”6.35 cm 7GNormal2-6/8”6.98 cm 7GLoose3-0”7.63 cm 12GTight1-3/8”3.49 cm 12GNormal1-4/8”3.81 cm 12GLoose1-5/8”4.12 cm

The 86th TIWC, Nov 18-21, 2008, Hong Kong 12 The three different tensions (tight, normal and loose) for three different gauges (5G, 7G and 12G) for five materials (acrylic, cotton, pima cotton, cashmere and wool) were converted into tightness factor so that fabric dimensions and fabric density can be compared, Table 2 shows results for acrylic fibre.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 13 Table 2 Knitting tension, loop length and tightness factor for acrylic fabric Machine Gauge Knitting Tension Yarn TexAverage loop length (mm) Tightness factor 5GTight GNormal GLoose GTight GNormal GLoose GTight GNormal GLoose

Results and Discussions

The 86th TIWC, Nov 18-21, 2008, Hong Kong 15 Fabric Dimensions and tightness Figures 1 & 2 showed the fabric dimensions under different tensions for different fibres for 5G fabric. Figure 1 showed that the courses per cm decease if the average loop length. In other words, the three different knitting tensions (tight, normal and loose) will affect fabric course density. The higher is the knitting tension (tight knitting), the smaller is the loop length and the higher is the course density.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 16 Figure 1: Courses per cm and loop length on 5G machine

The 86th TIWC, Nov 18-21, 2008, Hong Kong 17 Figure 2: Wales per cm and loop length on 5G machine

The 86th TIWC, Nov 18-21, 2008, Hong Kong 18 Both courses per cm and wales per cm (Fig. 1 & 2) show inversely relationship to fabric loop length under different knitting tension on these five different textile materials. Figure 3 showed this relationship with empirical formula after we plotted all data on the same chart. Figure 4 showed the stitch density (wales/cm X courses/cm) are inversely proportional to loop length square

The 86th TIWC, Nov 18-21, 2008, Hong Kong 19 Figure 3: Fabric density to loop length for these five textile materials in 5G machine

The 86th TIWC, Nov 18-21, 2008, Hong Kong 20 Figure 4: Stitch density to loop length square

The 86th TIWC, Nov 18-21, 2008, Hong Kong 21 Fabric dimensions and machine gauge The fabric dimensions (wales/cm and courses/cm) will be affected by machine gauge under different knitting tension as shown in Figure 5. It can be seen that both coarse gauge (5G) and fine gauge (12G) fabric samples show inversely relationship between loop length and courses/cm

The 86th TIWC, Nov 18-21, 2008, Hong Kong 22 Figure 5: Relationship between courses/cm and loop length on acrylic fabric for different gauges

The 86th TIWC, Nov 18-21, 2008, Hong Kong 23 Fabric dimensions and tightness factor In order to find out the effect of yarn count (tex), machine gauge on fabric dimensions, the fabric loop length is converted into tightness factor (TF). Tightness Factor = Sqrt(Tex)/loop length. Figure 6 show the tightness factor to loop length for the acrylic fibres under three different machine gauges.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 24 Acrylic Fiber Tightness Factor coru ses per cm 7 G 12G 5G Figure 6 Courses density to tightness factor on acrylic fibres

The 86th TIWC, Nov 18-21, 2008, Hong Kong 25 Fabric Pilling and Textile Materials Pilling is a fabric surface fault in which “pills” of entanglements fibres cling to the cloth surface, giving a bad appearance of garment. The International Fabricare Institute defines pilling as “the formation of small tangles of fibres or balls on the surface of fabric”.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 26 Fabric Pilling and Textile Materials Figure 7 showed the effect of fabric pilling for different textile materials on different machine gauges. It can be shown that textile materials play an important role on fabric pilling. The wool fibres give a lower pilling rate because of the scales nature of wool material which will trap the loose broken fibres on the fabric surface. Both cotton and cotton pima fibres give a higher pilling rate because of the smooth and fine surface of these cotton fibres. Only a small amount of broken fibres are shown on the surface and these loose fibres are easily fall off from the fabric surface.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 27 Figure 7 Pilling test for different fibres on different machine gauges

The 86th TIWC, Nov 18-21, 2008, Hong Kong 28 Pilling and Materials The relationship between pilling and machine gauge is not obviously to determine. For wool fabric, the coarser is the machine gauge (5G), the lower is the pilling rate as the open structure of coarse gauge machine will increase the number of broken fibres on the fabric surface.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 29 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 knitting tensions and machine gauge. Tightness factor is a good indicator to predict different yarn linear density and fabric loop length. Fabric pilling is directly affected by different textile fibres and wool fibres show a poor pilling than cotton fibre. However, no direct relationship between fabric pilling and machine gauge is found.

The 86th TIWC, Nov 18-21, 2008, Hong Kong 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.