WEFT WINDING PROCESS OR WEFT PREPARATION PROCESS
• Pirn or weft winding is the process of transferring of weft yarn on the small Pirn able to use in the shuttle of a loom.
• A tapered bobbin having weft yarn on it is known as Pirn.
• A Pirn is used on end feed shuttles.
• The pirn differs from bobbins in that the pirns are tapered.
Yarn passage in pirn winding machine:
• The yarn package ( cone or cheese) is mounted on the cone holder.
The yarn coming from package passes through a thread guide.
Now this yarn passes through a yarn tensioner. This tensioner impart required tension to the yarn and helps to regulate the yarn winding density on Pirn.
The yarn again passes through another thread guide now.
The yarn now passes through a yarn traverse guide. This traverse guide makes to and fro movement during winding process.
Yarn finally gets would upon the pirn.
WORKING PRINCIPLE OF PIRN WINDING MACHINE
• In weft winding machine, the Pirn is driven by a spindle.
In weft winding process a parallel winding packages results.
• Also, instead of winding them back and forth, the weaver winds them a half inch at a time.
• The pirn is mounted on the spindle driven by a mechanism which consists of gears and cam.
• The pirn rotates at very high and constant speed.
• When the diameter of Pirn increases. The yarn winding tension increases up to little extent due to less amount of yarn on the Pirn.
• When it rotates, it drags the yarn and winds on it.
• In pirn winding process a parallel winding packages results.
• This package comprises one or more threads which are laid very nearly parallel to the layers already existing on the package.
• The yarn receives to fro motion through yarn traverse guide.
• This yarn guide performs traversing motion of yarn.
• yarn traverse guide which makes nearly parallel coils of yarn on the Pirn
•Almost half inch of pirn ( chasing length) gets wound at a time.
• At a time the yarn moves to and fro between half inches distance of Pirn.
• When this half inches distance is filled, the winding of next half inches begins, thus winding of complete Pirn is performed.
• The the chasing length get shifted gradually during winding.
• The weft bobbin or Pirn contains very less amount of yarn length on it because it is very difficult to throw a shuttle with Pirn containing high amount of yarn on it.
Types of pirn winding machine:
• Ordinary Pirn winding machine
• Automatic Pirn winding machine
• Cop winding machine
DRAWBACKS OF PIRN WINDING MACHINE:
The main features of Pirn winding machine are given below:
• In Pirn winding machine, resulting (output) package is many times smaller than supply package.
• It is almost not capable to eliminate objectionable yarn faults during winding.
• Re-joining of yarn do not take place.
• Traverse has the characteristic of an oscillation in which the package diameter is controlled continuously.
• It necessitate to build bunch.
• At the time of beginning the winding tension is less. As the diameter increase, winding tension also rises.