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6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
PATTERNING POSSIBILITIES USING RACKING Constanta COMANDAR, Luminita CIOBANU ‘Gh. Asachi’ Technical University, Faculty of Textile & Leather Engineering Bd. Mangeron, 53, 700050, Iasi, Romania 1. Introduction Structural development of knitted fabrics is one of the most important parts of product development, especially in the case of new effects. Racking is common to all flat knitting machines and can be used to generate a particular group of effects based on inclined stitches. In practice the racking patterns are obtained based on rib evolutions with no patterns or with tuck stitches and miss stitches. Still, this patterning technique presents further design possibilities. There are two directions that can be taken into consideration for the development of racking patterns. One is the use of other evolutions than rib, including other patterns [1], [2] and the other direction is the use of different colours, in order to produce special colour effects [3]. The paper explores the two possibilities mentioned above by presenting interlock fabrics with racking patterns and colour effects and double-layer fabrics with connection through loops (tuck stitches) with racking patterns. The fabric structures and the structural effects in these examples are then characterised and discussed. 2. General considerations regarding racking patterns Racking patterns are obtained by changing the position of one bed in reference to the other. This will lead to the modification of stitch position from vertical to inclined, due to the fact that the inferior part of the stitch is connected to certain stitches in the opposite bed, while at its upper part, the next stitch connects with other stitches. Racking is a simple patterning technique, specific to flat knitting machines. It does not diminish productivity, due to the fact that is done between carrier movements. The fabrics are produced using rib evolutions and are characterised mainly by the stitch inclination that generates a zigzag effect. Racking patterns [4] are currently produced using rib evolutions, starting with 1x1 rib. The racking of the rear bed, normally 1 pitch, a number of times toward one direction and then in reverse generate the patterns. Apart normal stitches, tuck stitches and miss stitches can also be racked, so that the pattern is diversified. Based on specific yarn geometry, the racking effects can be divided into two main types: 2D and 3D effects. In the first case, the stitches are inclined only within the fabric plan. The basic 2D racking effect is caused by the fact that the inclined position of the rear stitch generates a torque that induces the inclination in the opposite direction of the corresponding front stitch. The two stitches are crossed without being transferred and because both stitches are inclined, the slope is increased. The correlation between the type of rib and the racking sequence leads to the annulment of the inclination (zigzag) effect in certain pattern areas. An interesting example is the 1x1 rib fabric with racking pattern presented in Figure 1.
Figure 1. 1x1 rib fabric with racking pattern
Another 2D racking effect is characterised by the fact that only the rear stitches are inclined, while the front stitches maintain their normal position.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
In the case of 3D racking effects, the presence of tuck stitches in a specific succession determines the fabric inclination toward opposite directions. As a consequence the fabric no longer can maintain its 2D geometry and is forced in a 3D geometry. The ‘egg nest’ fabric, created by Shima Seiki, is the most interesting example of such racking patterns. Figure 2 presents the knitting sequence.
Figure 2. “Egg nest” 3D racking effect
3. Experimental part The fabrics designed to illustrate the structural development possibilities for racking patterns were produced on a Shima Seiki flat knitting machine, gauge 7E. The interlock fabrics were knitted using 100% acrylic yarns, while the double-layer fabrics were produced with Modal microfibre from LENZIG, Austria. The fabric variants produced are presented in Table I.
Variant
Table I. Technological presentation of the fabric variants Racking Structure Raw material Knitting sequence effect
A1.1
Interlock 1x1
100% acrylic yarns, Nm 28/2/3
A1.2
Interlock 1x1
100% acrylic yarns, Nm 28/2/3
A2.1
Interlock 2x2
100% acrylic yarns, Nm 28/2/3
6th International Conference - TEXSCI 2007
A2.2
B1
B2
B3
Interlock 2x2
100% acrylic yarns, Nm 28/2/3
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
June 5-7, Liberec, Czech Republic
The interlock fabrics present racking patterns obtained by racking 1 pitch successively in opposite directions – variants A1.1 and A2.1 and by racking 1 pitch successively to one direction four times and in the opposite direction for another four times – variants A1.2 and A2.2. The interlock evolutions were produced with yarns of different colours for each rib evolution. The double-layer fabrics are characterised by two independent jersey fabrics, connected through loops on a limited number of wales. In the first variant B1 the fabrics are connected only by loops on the rear needles. The rear bed is racked successively 1 pitch to opposite directions for four times and then the racking are reversed. Variant B2 presents connecting loops on both beds. The racking succession is the same as for variant B1. In the case of variant B3 the connecting loops are first placed on the rear bed needles and the next row on the front bed needles. After each row there is 1 pitch racking in opposite directions. 4. Results and discussions In the case of the interlock fabrics, the combination between racking and colour patterns produces interesting effects. In the case of interlock 1x1 evolutions (see Figure 3.a), the successive racking in opposite direction generates a ‘chess table’ effect on the part that was racked (see Figure 3.c). On the opposite part the fabrics maintain their vertical stripes, as presented in Figure 3.b.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 3. Interlock 1x1 with 1 pitch successive racking in opposite direction and colour effects
If the racking is kept 4 times in each direction, the zigzag effect is different on the two fabric parts, as illustrated in the structural representation in Figure 4.a. On the part that was racked (rear) the effect is angled (see Figure 4.c), while on the other fabric part the effect is curved (see Figure 4.b). Both parts of the fabrics can be used in clothing.
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 4. Interlock 1x1 with multiple racking in the same direction and colour effects
The combination between successive opposite racking and colour patterns for interlock 2x2 evolutions maintains the same normal aspect on the fabric front (see Figure 5.b), while the “chess table” effect is combined with central vertical stripes, as presented in Figure 5.c. In the case of four 1 pitch racking in one direction followed by other four 1 pitch racking in opposite direction, the effect presented in Figure 5.b and 5.c is amplified by the two wales of the same colour. Figure 6 illustrates the front and rear aspect of the fabric.
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 5. Interlock 2x2 with 1 pitch successive racking in opposite direction and colour effects
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) Fabric - front aspect b) Fabric – rear aspect Figure 6. Interlock 2x2 with multiple racking in the same direction and colour effects
The double-layer fabrics are characterised by higher volume in the connecting area, due to tuck stitches and their inclined placement caused by racking. In comparison, the areas without connection are compact and the fabric is much thinner. It has to be emphasised that in first case the rear evolution is jersey with tuck loops from the front needles. This causes an interesting situation where, due to the fact that only the loop element is actually racked, the front stitches are drawn by the loops to even the generated tension and the rear stitches present no inclination. Figure 7 defines the situation for both parts in the case of variant B1.
a) Structural representation
b) Front aspect Figure 7. Variant B1
In the case of variant B2 and B3, the tuck loops are placed alternatively on the front and rear bed. The successive racking in one direction leads to an inclination effect visible only in the first row. The rest of the rows present no effect even if there was racking. The B2 fabric is characterised by the same aspect on both sides: a vertical strip of normal stitches and a patterned strip, as illustrated in Figure 8.a. Variant B3 has a similar structure, the difference consisting in the alternation of the patterned areas so to give chess table aspect for the fabric, presented in Figure 8.b.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) b) Figure 8. Fabric front aspect – variant B2 and variant B3
5. Conclusions Racking is a productive and efficient way of creating patterns and surface effects on flat knitting machines. These examples show the potential development solutions especially regarding new structural effects. The use of evolutions other than rib – interlock and tubular – opens a range of interesting racking effects. By combining racking patterns with colour patterns one can obtain a diverse range of colour motifs and effects. The paper presents the following new aspects for racking patterns. The first aspect concerns the use of colours and racking patterns for interlock evolutions. The second new aspect proposed by the authors is about use of racking techniques in the case of the double layer fabrics. From this experimental work it resulted a new case of stitch geometry in racking patterning: the rear stitches that are actually racked are keeping their normal position, while the front stitches are inclined. Such fabrics can be used in garments for cold season, especially products where the colour and relief effects are targeted and for products with two faces that present different properties due to the double layer structure and different raw materials. Acknowledgements The present investigation was conducted with the financial support of the National University Research Council CNCSIS, within the research grant A 437/2006. The authors wish to thank the LENZIG Company for their cooperation and help. References 1. Mulhau, G.J., RRG-Bindungen bei der Flachstricktechnik, part 1, Wirckerei und Strickerei Technik, 9/1992, p. 812-814 2. Mulhau, G.J., RRG-Bindungen bei der Flachstricktechnik, part 2, Wirckerei und Strickerei Technik, 11/1992, p. 1044-1046 3. Comandar, C., Ciobanu, L., Knitted fabrics with racked patterns, 5th International Textile Conference, Istanbul, May, 2005, paper on CD 4. Comandar, C., Structura si proiectarea tricoturilor: tricoturi din batatura, Ed. Cermi, Iasi, 2000
June 5-7, Liberec, Czech Republic
PATTERNING POSSIBILITIES USING RACKING Constanta COMANDAR, Luminita CIOBANU ‘Gh. Asachi’ Technical University, Faculty of Textile & Leather Engineering Bd. Mangeron, 53, 700050, Iasi, Romania 1. Introduction Structural development of knitted fabrics is one of the most important parts of product development, especially in the case of new effects. Racking is common to all flat knitting machines and can be used to generate a particular group of effects based on inclined stitches. In practice the racking patterns are obtained based on rib evolutions with no patterns or with tuck stitches and miss stitches. Still, this patterning technique presents further design possibilities. There are two directions that can be taken into consideration for the development of racking patterns. One is the use of other evolutions than rib, including other patterns [1], [2] and the other direction is the use of different colours, in order to produce special colour effects [3]. The paper explores the two possibilities mentioned above by presenting interlock fabrics with racking patterns and colour effects and double-layer fabrics with connection through loops (tuck stitches) with racking patterns. The fabric structures and the structural effects in these examples are then characterised and discussed. 2. General considerations regarding racking patterns Racking patterns are obtained by changing the position of one bed in reference to the other. This will lead to the modification of stitch position from vertical to inclined, due to the fact that the inferior part of the stitch is connected to certain stitches in the opposite bed, while at its upper part, the next stitch connects with other stitches. Racking is a simple patterning technique, specific to flat knitting machines. It does not diminish productivity, due to the fact that is done between carrier movements. The fabrics are produced using rib evolutions and are characterised mainly by the stitch inclination that generates a zigzag effect. Racking patterns [4] are currently produced using rib evolutions, starting with 1x1 rib. The racking of the rear bed, normally 1 pitch, a number of times toward one direction and then in reverse generate the patterns. Apart normal stitches, tuck stitches and miss stitches can also be racked, so that the pattern is diversified. Based on specific yarn geometry, the racking effects can be divided into two main types: 2D and 3D effects. In the first case, the stitches are inclined only within the fabric plan. The basic 2D racking effect is caused by the fact that the inclined position of the rear stitch generates a torque that induces the inclination in the opposite direction of the corresponding front stitch. The two stitches are crossed without being transferred and because both stitches are inclined, the slope is increased. The correlation between the type of rib and the racking sequence leads to the annulment of the inclination (zigzag) effect in certain pattern areas. An interesting example is the 1x1 rib fabric with racking pattern presented in Figure 1.
Figure 1. 1x1 rib fabric with racking pattern
Another 2D racking effect is characterised by the fact that only the rear stitches are inclined, while the front stitches maintain their normal position.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
In the case of 3D racking effects, the presence of tuck stitches in a specific succession determines the fabric inclination toward opposite directions. As a consequence the fabric no longer can maintain its 2D geometry and is forced in a 3D geometry. The ‘egg nest’ fabric, created by Shima Seiki, is the most interesting example of such racking patterns. Figure 2 presents the knitting sequence.
Figure 2. “Egg nest” 3D racking effect
3. Experimental part The fabrics designed to illustrate the structural development possibilities for racking patterns were produced on a Shima Seiki flat knitting machine, gauge 7E. The interlock fabrics were knitted using 100% acrylic yarns, while the double-layer fabrics were produced with Modal microfibre from LENZIG, Austria. The fabric variants produced are presented in Table I.
Variant
Table I. Technological presentation of the fabric variants Racking Structure Raw material Knitting sequence effect
A1.1
Interlock 1x1
100% acrylic yarns, Nm 28/2/3
A1.2
Interlock 1x1
100% acrylic yarns, Nm 28/2/3
A2.1
Interlock 2x2
100% acrylic yarns, Nm 28/2/3
6th International Conference - TEXSCI 2007
A2.2
B1
B2
B3
Interlock 2x2
100% acrylic yarns, Nm 28/2/3
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
Double-layer with loop connection
Modal microfibre Nm 32/2/3 50% Modal + 50% Cotton , Nm 40/32/2
June 5-7, Liberec, Czech Republic
The interlock fabrics present racking patterns obtained by racking 1 pitch successively in opposite directions – variants A1.1 and A2.1 and by racking 1 pitch successively to one direction four times and in the opposite direction for another four times – variants A1.2 and A2.2. The interlock evolutions were produced with yarns of different colours for each rib evolution. The double-layer fabrics are characterised by two independent jersey fabrics, connected through loops on a limited number of wales. In the first variant B1 the fabrics are connected only by loops on the rear needles. The rear bed is racked successively 1 pitch to opposite directions for four times and then the racking are reversed. Variant B2 presents connecting loops on both beds. The racking succession is the same as for variant B1. In the case of variant B3 the connecting loops are first placed on the rear bed needles and the next row on the front bed needles. After each row there is 1 pitch racking in opposite directions. 4. Results and discussions In the case of the interlock fabrics, the combination between racking and colour patterns produces interesting effects. In the case of interlock 1x1 evolutions (see Figure 3.a), the successive racking in opposite direction generates a ‘chess table’ effect on the part that was racked (see Figure 3.c). On the opposite part the fabrics maintain their vertical stripes, as presented in Figure 3.b.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 3. Interlock 1x1 with 1 pitch successive racking in opposite direction and colour effects
If the racking is kept 4 times in each direction, the zigzag effect is different on the two fabric parts, as illustrated in the structural representation in Figure 4.a. On the part that was racked (rear) the effect is angled (see Figure 4.c), while on the other fabric part the effect is curved (see Figure 4.b). Both parts of the fabrics can be used in clothing.
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 4. Interlock 1x1 with multiple racking in the same direction and colour effects
The combination between successive opposite racking and colour patterns for interlock 2x2 evolutions maintains the same normal aspect on the fabric front (see Figure 5.b), while the “chess table” effect is combined with central vertical stripes, as presented in Figure 5.c. In the case of four 1 pitch racking in one direction followed by other four 1 pitch racking in opposite direction, the effect presented in Figure 5.b and 5.c is amplified by the two wales of the same colour. Figure 6 illustrates the front and rear aspect of the fabric.
a) Structural representation b) Fabric - front aspect c) Fabric – rear aspect Figure 5. Interlock 2x2 with 1 pitch successive racking in opposite direction and colour effects
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) Fabric - front aspect b) Fabric – rear aspect Figure 6. Interlock 2x2 with multiple racking in the same direction and colour effects
The double-layer fabrics are characterised by higher volume in the connecting area, due to tuck stitches and their inclined placement caused by racking. In comparison, the areas without connection are compact and the fabric is much thinner. It has to be emphasised that in first case the rear evolution is jersey with tuck loops from the front needles. This causes an interesting situation where, due to the fact that only the loop element is actually racked, the front stitches are drawn by the loops to even the generated tension and the rear stitches present no inclination. Figure 7 defines the situation for both parts in the case of variant B1.
a) Structural representation
b) Front aspect Figure 7. Variant B1
In the case of variant B2 and B3, the tuck loops are placed alternatively on the front and rear bed. The successive racking in one direction leads to an inclination effect visible only in the first row. The rest of the rows present no effect even if there was racking. The B2 fabric is characterised by the same aspect on both sides: a vertical strip of normal stitches and a patterned strip, as illustrated in Figure 8.a. Variant B3 has a similar structure, the difference consisting in the alternation of the patterned areas so to give chess table aspect for the fabric, presented in Figure 8.b.
6th International Conference - TEXSCI 2007
June 5-7, Liberec, Czech Republic
a) b) Figure 8. Fabric front aspect – variant B2 and variant B3
5. Conclusions Racking is a productive and efficient way of creating patterns and surface effects on flat knitting machines. These examples show the potential development solutions especially regarding new structural effects. The use of evolutions other than rib – interlock and tubular – opens a range of interesting racking effects. By combining racking patterns with colour patterns one can obtain a diverse range of colour motifs and effects. The paper presents the following new aspects for racking patterns. The first aspect concerns the use of colours and racking patterns for interlock evolutions. The second new aspect proposed by the authors is about use of racking techniques in the case of the double layer fabrics. From this experimental work it resulted a new case of stitch geometry in racking patterning: the rear stitches that are actually racked are keeping their normal position, while the front stitches are inclined. Such fabrics can be used in garments for cold season, especially products where the colour and relief effects are targeted and for products with two faces that present different properties due to the double layer structure and different raw materials. Acknowledgements The present investigation was conducted with the financial support of the National University Research Council CNCSIS, within the research grant A 437/2006. The authors wish to thank the LENZIG Company for their cooperation and help. References 1. Mulhau, G.J., RRG-Bindungen bei der Flachstricktechnik, part 1, Wirckerei und Strickerei Technik, 9/1992, p. 812-814 2. Mulhau, G.J., RRG-Bindungen bei der Flachstricktechnik, part 2, Wirckerei und Strickerei Technik, 11/1992, p. 1044-1046 3. Comandar, C., Ciobanu, L., Knitted fabrics with racked patterns, 5th International Textile Conference, Istanbul, May, 2005, paper on CD 4. Comandar, C., Structura si proiectarea tricoturilor: tricoturi din batatura, Ed. Cermi, Iasi, 2000
