Warp knitting

warp knitting machine

1. Prepared by Rasmin Thahani Z, Assistant Professor, Syed Ammal Arts and Science College, Ramanathapuram . TEXTILE SCIENCE WARP KNITTING

2. WARP KNITTING Warp knitting is a method of fabric formation in which the loops are made in a vertical way along the length of the fabric from each warp yarns.  Thus, there will be a needle for each yarn. The knitted stitches in warp knit fabrics have a crisscross diagonal appearance which feels smoother than weft knits. Warp knitting differs from weft knitting, basically in that each needle loops its own thread.

3. WARP KNITTING – contd.. The needle produce parallel rows of loops simultaneously that are interlocked in a zigzag pattern. The stitches on the face of the fabric appear vertically, but at a slight angle and the back appear horizontally as floats at a slight angle. These floats called laps, or underlaps are called laps or underlaps are a distinguishing identification of warp knits.

4. PROPERTIES It shows less elasticity than weft knitting. It becomes favorable over weft in properties like soft and drapery, higher density, warm to wear.  Through this process many different types of yarn can be processed like combed, staple, carded and filament which is not possible with weft knitting. It may be flat or tubular and can be produced in many varieties of patterns. It can yield cloth with a dimensional stability almost equal to that of woven fabrics.

5. Classification of Warp Knitted Fabrics

6. Classification of Warp Knitted Fabrics

7. TRICOT KNIT The word tricot comes from the French word “Tricoter” which  means to knit. Each set of yarns from a warp beam is fed to a row of needles arranged across the width of the machine and is controlled by yarn guides set in a guide bar that is also laid across the machine.

8. PROPERTIES Tricot fabrics have many good attributes. They are porous and permit passage of water vapor and air for body comfort. They also offer bulk without undue weight. Tricot fabrics are soft, wrinkle resistant, and have good drapability.

9. PROPERTIES They have controllable elasticity and they do not run or fray. Tricot construction contributes to good abrasion resistance and high bursting and tearing strength. Other factors that contribute to the fabrics strength are the fiber and yarn structure.

10. USES Tricot knits are used for a wide variety of fabric weights and designs. Typical uses of tricot fabrics are lingerie, lounge wear, sleep wear, blouses, shirts, dresses, slacks, uniforms for nurses and waitresses, bonded fabric material, outer wear and automobile upholstery. These fabrics may be identified by type.

11. TRICOT WARP KNITTING MACHINE In tricot warp knitting machine compound needles are used. The warp yarns are feed to the needles through guide bars using shogging and swinging motion. Normally tricot warp knitting machine is used for fashion fabrics, mesh fabrics.

12. TRICOT WARP KNITTING MACHINE - contd Modern tricot machines are constructed with compound needles, while in the past tricot machines were equipped with beard needles. Tricot machines are commonly equipped with from two to four yarn guide bars and require the same number of warps to be used.

13. Tricot warp knitting machine

14. RASCHEL KNIT The raschel knit ranks in importance of production with tricot, but it surpasses it in variety of products, which range from veilings and laces to power nets for foundation garments to such pile fabrics as carpets. The raschel knit is made with latched needles rather than the bearded type used for tricot, Milanese and simplex.

15. RASCHEL KNIT The raschel fabrics can usually be distinguished from tricot fabrics in that raschel constructions are made with heavy yarns and usually have an intricate, lacelike pattern, whereas tricot constructions are made with fine yarns and are either flat or have a simple geometric pattern. Raschel

16. PROPERTIES Raschel machines are extremely versatile. They can knit every type of yarn made of any kind of fiber, including metallic and glass, and in any form, whether staple or filament, standard or novelty. Knits can be lacy, highly patterned and even piled. 

17. PROPERTIES It includes a fabric which can be dense or compact, open or lofty, stable or stretchy, single faced or reversible . It can be identified by their intricate designs. The use can be in almost any garment due to high customization of the raschel machine from lightweight lace to heavy chenille . The machines can produce both flat and tubular warp knit fabrics. 

18. USES Made from heavier yarns, Raschel knits are used for manufacturing versatile and flexible fabrics. These are more textured and can be used for a wide range of  technical textile applications . Such as- automotive textiles, home textiles, lingerie, mosquito nets, lightweight coating substrates, sportswear/swimwear, lining fabrics, outerwear, etc . Different types of single and double needle bar Raschel machines are built today for the production of a wide variety of products ranging from sacks to artificial blood vessels.

19. USES Such as- automotive textiles, home textiles, lingerie, mosquito nets, lightweight coating substrates, sportswear/swimwear, lining fabrics, outerwear, etc. Different types of single and double needle bar Raschel machines are built today for the production of a wide variety of products ranging from sacks to artificial blood vessels. Seamless tubular fabrics, pile fabrics and many other special fabrics can easily be produced in double needle bar machine by using 4 to 6 guide bars. 

20. USES But by using more number of guide bars (16 and above), production of branching tubular fabrics such as artificial blood vessels, patterned panty-hose etc. and shaped innerwear is no more a problem. Warp knitted spacer fabric (WKSF) is a three-dimensional textile which is also made by a double-needle bar Raschel machine.

21. RASCHEL WARP KNITTING MACHINE Raschel warp knitting machine may be made with either single needle bar or double needle bar. In Raschel, yarns coming from the beam as parallel sheet are converted into fabric by loop formation before being wound in open width form on the cloth roller .

22. RASCHEL WARP KNITTING MACHINE Nowadays Raschel machines are available with weft insertion facility . Raschel Warp Knitting Machine is used for lace  fabric and trimming. It is also used to produce in outdoors and military fabrics for products such as backpacks.

23. Raschel Warp Knitting Machine

24. MILANESE KNIT Milanese knit is made of two sets of yarns knitted diagonally. The face side has fine vertical rib and the reverse has a diagonal structure. The Milanese stitch, though accomplished by a different technique, produces a fabric very similar in appearance to tricot. It can be identified by the fine rib on the face and a diagonal pattern on the back.

25. MILANESE KNIT – contd.. Milanese is knitted on the flat bed machine with spring beard needles and on the circular machine with latch needles. It is usually knitted from filament yarn into fine light weight fabrics. Milanese

26. PROPERTIES It is lightweight, drapery, smooth and is mostly used for gloves . Milanese fabric are superior to tricot in smoothness, elasticity, regularity of structure and split and tear resistance.

27. DIFFERENCE BETWEEN TRICOT AND RASCHEL WARP KNITTING MACHINE

28. Tricot Knit Raschel Knit In the past, bearded needle was used but now a days compound needle used Rachel m/c used latch needle together with a wire or blade M/C gauge expressed in needle per inch M/C gauge expressed in needle/inch Chain link numbering  0, 1, 2, 3, ….etc Chain link numbered in even numbers 0, 2, 4, ….etc Three links per course 2 links per course Function of sinker is holding down, knocking and supporting the fabric Sinker performs the function of holding down the loops whilst the needle rise The sinker are joined to each other at the front and back The sinker are not joined together by a lead across their ends nearest to the needle bar

29. Tricot Knit Raschel Knit The sinker never move clear of needles They can move clear of the needles towards the back of the m/c for the rest of the knitting cycle The fabric is drawn away towards the batching roller almost at right angles to the needle bar The fabric is drawn downwards from the needles almost parallel to the bar at an angle of 120°-160° The warp beams are accommodated in an inclined arc towards the back of the m/c there the top The warp beams are arranged above the needle bar centered over the rocker shaft The warp sheets pass over the top of the guide bar rocker shaft to their tension The warp sheets pass down the guide bar

30. Tricot Knit Raschel Knit Mechanical attention is carried out at the front of the m/c Mechanical attention is carried out at the back of the m/c The guide bars are numbered from the back towards the front of the m/c The guide bars are numbered from front of the m/c High speed production Low speed production