Monday, March 2, 2020

WORKING PROCEDURE OF RING FRAME MACHINE


WORKING PROCEDURE OF RING FRAME MACHINE:

The working procedure of ring frame machine can be understand in the following steps:

CREELING:

The roving bobbins obtained from simplex process is used as feed material in the ring frame. These roving bobbins are mounted on the bobbin holders of creel. The creel is mounted on the top of the ring frame machine. The roving now passes through guide bar which guides it toward the drafting system. The creel is equipped with automatic roving break stop motion. When roving break occurs in any spindle during process, the stop motion actuates immediately and stops the working of that particular spindle.

DRAFTING:

When the roving gets entered into the drafting zone, it is drafted according to desired count of yarn to be spun. The drafting system is inclined at 45-50 degree in the ring frame machine. The working performance of a drafting system of ring frame greatly affects the yarn quality.

The amount of draft to be employed in the ring frame depends upon the material to be processed. It normally ranges between 35 - 40 in processing of cotton fibres and up to 50 in processing of synthetic material. The drafting system plays very important role in the performance of ring frame process. The  higher draft range of ring frame machine helps to reduce the yarn cost because coarser roving can be used. Thus operation cost in simplex gets reduced. The drafting rollers are loaded with spring pressure to maintain the regular gripping of rollers.

Due to less number of fibres in the front drafting zone, the fibre strand has very poor strength. This situation necessitates  to provide enough guidance to the drafted material. This guidance is performed with the help of aprons. The double apron drafting arrangements with longer bottom aprons is the most widely used in guiding system in all the modern ring frame machines.  In order to be able to guide the fibres, the upper apron must be pressed with controlled force against the lower apron. A controlled spacing (exit opening), precisely adapted to the fibre volume is needed between the two aprons at the delivery for controlled force against bottom aprons. The long bottom aprons have the advantage in comparison with short aprons. The long aprons can be easily replaced when it gets  damaged and there is less risk of choking with fluff.

TWISTING:

When the drafted fibres strand comes out from the front drafting rollers, it has very poor strength. A certain amount twist is inserted into the fibres strand. This twist helps to hold the fibres together in the yarn. The twist is inserted to the yarn by spindle rotating at very high speed. The traveller rotating on the spinning ring inserts one turn into the yarn after completion of each revolution.

WINDING:

The yarn producing during ring spinning process gets wound on the ring bobbin simultaneously and continuously. This job is performed by the speed difference between spindle and traveller. The traveller drags with spindle with the help of attached yarn to it. The traveller rotates at lower speed than spindle. The yarn gets wound on a ring bobbin. The  traveller imparts twist to the yarn. The traveller and spindle together help to wind the yarn on the bobbin. The length wound up on the bobbin corresponds to the difference in peripheral speeds of the spindle and traveller.  The difference in speed should correspond to length delivered at the front drafting rollers. Since traveller does not have it's own drive, it gets  dragged along behind by the spindle.

A yarn traverse guide is mounted on the movable ring rail. This traverse guide carries the yarn upward and downward during package formation. The traverse guide makes up and down movement with movable ring rail. The layer traverse of the ring rail is also less than the full winding height of the empty ring bobbin. The ring rail therefore has to be raised slightly (shift traverse) after each layer has been wound.

A high balloon results in large bobbin diameter leading to space problems. The larger balloon creates higher air drag on the yarn. Thus higher yarn tension acts on the yarn which results in the form of more end breakages during ring frame process. In order to avoid this problem, balloon control rings are used. It divides the balloon into two smaller sub-balloons. Inspite of its large overall height, the double-balloon created in this way is thoroughly stable even at relatively low yarn tension.  Balloon control rings therefore help to run the machine with long spindles (longer lift) and at high spindle speed, but with lower yarn tension.

DOFFING:

Doffing is the process of replacing the filled ring bobbins by empty bobbin. When the ring bobbins get full of yarn, these bobbins need to replace with empty bobbins. This job gets performed manually. It can be done automatically also. When doffing is performed, the machine is stopped first then thread guides are hinged up. Now bobbins are removed from the spindles and empty bobbins are put on the spindles. The thread guides are lowered again and machine is restarted.

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