Features and Uses of the Raschel Warp Knitting Machine
B.J.Group, Mawna, Gazipur
There are various types of knitting machine. Warp knitting machines are categorized on the basis of construction of different machine parts and their operations. Tricot and Raschel are two main categories of machine. Further classification of warp knitting is given in Fig-1. Among those Raschel knitting machine is one of the most important knitting machines to produce knitted fabric. 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. Nowadays Raschel machines are available with weft insertion facility. Raschel Warp Knitting Machine is used for lace fabric and trimmings. It is also used to produce in outdoors and military fabrics for products such as backpacks.
Main Features of the Raschel Warp Knitting Machine:
Raschel warp knitting machines have the following important features:
1. Raschel machines used latch needles together with a latch wire or blade.
2. Raschel machines have a gauge expressed in needles per two inches (5cm) so that for example, a 36 gauge Raschel will have 18 needles per inch.
3. Their chain links are usually numbered in even numbers 0, 2, 4, 6, 8 etc., generally with two links per course.
4. Raschel sinkers only perform the function of holding down the loops whilst the needles rise.
5. Raschel sinkers are not joined together by a lead across their ends nearest to the needle bar so they can move away to wards the back of the machine for the rest of the knitting cycle.
6. The needle trick-plate verge acts as a fabric support ledge and knock-over surface.
7. The fabric is drawn downwards from the needles almost parallel to the needle bar at an angle of 120 to 160 degrees by a series of take-down rollers.
8. The warp beams are arranged above the needle bar centred over the rocker shaft so that warp sheets pass down to the guide bars on either side of it.
9. The beams are placed above the machine so it is accessible at the front for fabric inspection and at the back for mechanical attention to the knitting elements.
10. The guide bars are threaded commencing with the middle bars and working out wards from either side of the rocker shaft.
11. The guide bars are numbered from the front of the machine.
12. With the Raschel arrangement there is accommodation for at least four 32 inch diameter beams or large numbers of small diameter pattern beams.
13. The accessibility of the Raschel machine, its simple knitting action and its strong and efficient take-down tension makes it particularly suitable for the production of coarse-gauge openwork structures employing pillar stitch and inlay lapping variations and partly-threaded guide bars which are difficult to knit and hold down with the tricot arrangement of sinkers.
14. Additional warp threads may be supplied at the selvedges to ensure that these needles knit fabric, otherwise a progressive press-off of loops may occur.
Uses of Raschel Warp Knitting Machine:
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. 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. 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.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.