POSITIVE YARN FEEDING & How it affects to the fabric quality

GROUP MEMBERS Narampanawa R. D. B Nishshanka N. A. K. P. N Pahathkumbura D. K. B Ranasinghe D. D

YARN FEEDING SYSTEMS NEGATIVE YARN FEEDING POSITIVE YARN FEEDING The needle draws yarns directly from the package (Beam, Cone etc…) An external element decides the yarn length released to the needle

DRAW BACKS OF NEGATIVE YARN FEEDING Feed rate (amount of yarn) and Yarn tension will be vary from yarn to yarn Decrease the fabric quality. Yarn breakages Reduction in production efficiency.

POSITIVE YARN FEEDING Avoid drawbacks as non uniform Feed rates and Yarn tension variations How? The positive feed units usually driven by external force (motor, gear driven) rather than by the needles, extract yarns from the packages and deliver them to the needles.

POSITIVE YARN FEEDING SYSTEM Tape feed mechanism Yarn storage feeder Positive storage yarn delivery device

TAPE FEED SYSTEM Each yarn from the package is passed in between its own Feed Wheel and the Drive Tape

Continued…….. This is commonly used in circular knitting machines. By changing the Quality Adjusting Pulley diameter, yarn delivery speed can be alter.

Drawbacks Due to slippage of the yarn in between drive tape and the feed tape, yarn feed rate can be affected. Deformed loops will be formed from this knitting system. Quality Wheel can not be adjusted while machine been operated Yarn faults cannot be detected before the knitting zone.

Yarn Storage Feeder This system is used when the structure differs from knitting system to knitting system and from course to course within the pattern (ex : multi color jacquard)

Drawbacks Does not feed the yarn to the needle as a fully positively feeding system. (only up to the temporary storage)

Positive storage yarn delivery device This is a combination of tape feeder and the yarn storage.

Positive storage yarn delivery device…

Positive storage yarn delivery device… Detect yarn faults before entering to the knitting zone. Increase the efficiency Reduce needle breakages

Fabric quality through positive yarn feeding Provide the foundation for the plating technique. Controls the fabric properties ( gsm, composition, performance such as stretch ability) Faults of yarn are detected prior to knitting zone which reduce defects of the fabric. Uniform stitches give better fabric appearance.

Function Feed rate tape selector Vibrating yarn tensioner prevents the build up of dirt between the tension rings and prevent false stoppage. A magnetic tension ring applies a uniform tensioning force . Anti-filamentation unit In filament yarns capillary filaments can collect on the winding reel. This is prevented by selecting the correct take off position. Winding reel There different winding reels Closed wheel – prevents filament building Thread wheel - in case of irregular thread consumption

Function Feed Rate Tape Selector – gives the correct amount of for each course. Ex : Half Milano In here yarn is constantly fed in the positive feed Mode.

Function Friction Drive Mode - On machines with variable yarn consumption (e.g. drop stitch pattern or mini Jacquard machines), this should be run in the friction mode. But this still can not be used for complex structures where the yarn consumption differs from knitting system to knitting system.

Developments of positive yarn feeders i-DSCS, Digital Stitch Control System "with Intelligence from Shima Seiki." i-DSCS has the capability to actively control yarn-feed in both feed and retrieval directions as necessary. This is crucial to the precision knitting required in WHOLEGARMENT production.

Developments of positive yarn feeders In seamless knitting and new warp knitting machines have storage feeders. New storage feeders (Rojtricot) has an additional yarn twisting and has a switch for setting the rotational direction for S or Z twist yarns. A braking system at the end of the package body ensures that the yarn tension is uniform.

Developments of positive yarn feeders ►This operates continuously, without starting and stopping. The adjustable conical magnetic tensioner at the yarn outlet detect the tension and drive according to it maintain constant yarn tension. ► Microprocessor is used to calculate the average yarn usage rate and adjust the motor speed to the yarn usage accordingly.

True Positive Feeding Modern Garment shaping and Technical fabric knitting machines with patterning requires different loop lengths for different needles for each course in the fabric.

TPF This system widely uses in medical textiles such as Scan-to-knit. Above system fulfills that requirement How? pre-calculate the yarn requirement and deliver the changing yarn requirement in synchrony with the feeder movement

TPF Ctd… Course-by-course needle selection program detailing the action of each needle across the needle beds Accesses this data, pre-calculates the yarn requirement in real time as the carriage traverses the needles and supplies the appropriate control signals to the drive motors

Positive Feeding on Warp Knitting Yarn beams are rotated by means of mechanical and electronic systems to give exact runner lengths uniformly.

Warp Knitting Cone and Drum mechanism is used in mechanical systems Electronically geared motors are used in modern systems with the feelers.

Problem areas of positive yarn feeders Yarn breakages due to friction dust, that have filaments protruding from the yarn, that carry a relatively large amount of sizing, or that in some other way leave behind or cause traces or deposits on parts of the yarn feeder will cause an irregular feeding of the yarn and will cause a null effect on the positive yarn feeding. With the additional force given, yarn properties be affected

Problem areas of positive yarn feeders The nip roller positive feeding will require a complex yarn path – Influences the design of the machine

Problem areas of positive yarn feeders Large fluctuations caused by individual needle selection cannot be adopted through positive feeding ( large area jacquards) Due to intensive individual attention towards each and every yarn been fed

Overcoming them It is the object to create a yarn feeder whose operation properties are largely independent of the nature of the yarn. This object is attained by a yarn feeder having a yarn feed wheel with a special geometry that facilitates the feeding and payout of yarn onto and from the yarn feed wheel.

Yarn feeder with a ceramic coated wheel Ceramic coated spikes Yarn

Minimizes the effect by the heat Friction will be at a controlled level of affection Will make a yarn feeder, independent from the yarn path

Change from the initial nip roller to the tape positive feeding system Cheaper Adaptable Simpler

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