1. POSITIVE YARN FEEDING & How it affects to the fabric quality

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

3. 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

4. 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.

5. 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.

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

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

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

9. 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.

10. 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)

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

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

13. Positive storage yarn delivery device…

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

15. 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.

16. 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

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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

24. 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

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

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

27. 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

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

29. 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

30. 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.

31. Yarn feeder with a ceramic coated wheel
Ceramic coated spikes
Yarn

32. 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

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

34. THANK YOU