Yarn feeding process in knitting machine
In a knitting cycle, yarn feeding is commonly fed at the same time as the needle is raised for clearing and the hook is open. For non-stop knitting, yarn is to be supplied or fed to the needles or to the knitting zone continuously. In weft knitting, yarn is usually provided from cones or other appropriate yarn packages located in a creel.
The yarn is taken down from the spool organized on a unique holder called creel if located beside the machine, or rack if placed above it. The yarn is then guided into the knitting zone through the thread guide, which is commonly a small plate with a steel eyelet for the yarn. In order to acquire particular designs along with intarsia and vanise effects, the machines are prepared with special thread guides.
Flow Chart of yarn :
Ceramic Eye Pot
Previous Sensor Guide
After Sensor Guide
Ceramic Eye Pot
The principals involved in supplying of yarn may be summed as follows:
- Negative feeding
- Positive Feeding
Yarn is pulled through the needles directly from the package through guides, tensions, etc. It does now not require any extra attachment as yarn is drawn automatically due to the knitting process. This approach does not maintain uniform yarn tension. But it can easily alter and deal with the difference in stitch cam setting in different feeds
In the case of positive feeding, the yarn is first measured as required and then supplied to the needle or knitting zone. This technique makes it possible to supply equal lengths of yarn to all feeds and maintain uniform tension of the input yarn. The result is a uniform loop length and a better quality of the fabric. However, this technique requires a special attachment to the machine. Construction of a common positive feeder. To measure the yarn before entering the weaving zone, drums or cylinders (M) is measured in each feeding zone.
In order to make equal loop length in every course, all the measuring drums are rotated at the same surface speed by means of a common belt. The belt is usually made of PIV. From the pulley (P) which is sometimes called the control drive wheel. The effective diameter of this palli can vary in infinite steps as required. The yarn passes through the nip formed by the measuring drum and belt and moves to the knitting zone at the rate of movement of the surface of the measuring drum. The cam setting is changed by changing the length of the loop, while the surface speed of the measuring drum is changed by separating the effective diameter of the driving pulley. The adjustment of the position of the pulley (A and D) maintains the required tension on the belt. As the yarn passes between a rotating drum and the driving tape/belt, the yarn may be partly damaged. The yarn by this system depends on the tension offers
a) Count and evenness of the yarn,
b) Running behavior of the yarn,
c) Type of yarn, particularly spun yarn or filament yarn. So the positive feed is unsuitable
As the measurement of the exact requirement of yarn is to some extent difficult and needs very accurate and adjustable attachment, a storage device may be used for feeding the yarn instead of a positive feeder. Storage feeder supply yarn at a uniform tension rather than at a uniform rate of feed and is thus suitable for a wide range of yarn feed. Suitable for a wide range of feed rates and thus yarn feeds.
In this case, yarn is first withdrawn from the package and wound tangentially as equally spaced coils on a store (drum) and The needles then draw the yarn from the store which allows the yarn to deliver uniform tension. The most popular IRO storage feeder operating policy in this field, the yarn from the yarn package comes first Wound in a specially sized rotating drum or cylinder coil by coil. As soon as the drum is filled with yarn coils, a photo-electric or capacitance type sensor stops the drum. When a certain amount of yarn is delivered to the knitting zone from the drum automatically starts rotating for winding further length of yarn. The yarn from the drum surface is withdrawn gently coil by coil by the needles through a floating nip formed by the bottom edge of the drum and nylon bristled ring in constant low tension. The yarn is prevented from slipping off the drum by the tension ring. The nylon-bristled rings of different colors are generally used to vary the yarn tension.
Combined positive and storage feeding:
Further development is the combination of positive feed and storage feed with a choice of modes available through the clutch. In this case, the yarn path is not guided by tape or belt but is hit directly on the drum. In this case a notched pulley is provided at the top of the drum which can be detached from the drum if required. The drum is made of PIV. Run with tape or belt that passes over the pulley and the yarn is deposited or wound on the drum surface at a constant rate. The yarn is withdrawn from the drum with needles according to their requirements.