Sunday, June 27, 2021

Yarn twist testing

 

Please click on the below link to read this article in Hindi:

यार्न ट्विस्ट टेस्ट

Yarn twist test:


YYarn twist (Degree of twist):


T The yarn twist is a very important parameter. The number of turns of twist required to hold the fibres and yarns together is called the degree of yarn twist. it is measured in turns per inch in the yarn. 
The amount of twist or degree of twist seriously affects the performance of yarn. If the yarn has less twist than standard then fibre slippage may occur. The yarn has a low twist possess low strength. There may be a chance of pilling formation due to low twists. It will give a soft feel and touch. If the yarn has more twists than standard. The yarn will show good strength but it will give a rough feel and touch. There may be a chance of snarling too.
the types of twists used in the yarn are given below:

     S-twist:

The clockwise twist of yarn is called s-twist. The inclination of fibres in yarn looks similar to the middle part of the English letter “S”.

 Z-twist:

The anticlockwise twist of yarn is called z-twist. The inclination of fibres in the yarn looks similar to the middle part of the English letter Z.



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Yarn twist testing method:


Apparatus used:


1 - Yarn twist tester
2 - Yarn package
3 - Magnifying glass
4 - Needle

Structure of yarn twist tester:



The fixed jaw is mounted on the right side of the table. The rotating shaft is mounted on this fixed jaw. This shaft is mounted on the bearings. It gets free to move in any direction. A rotating thread clamp is fitted at the left hand of this rotating shaft.  The spur gear is mounted at the right side of this rotating shaft. The handle is mounted near the perimeter of this spur gear.  This spur gear gets engaged with other gear mounted on the shaft of the counter meter. 

The sliding jaw is mounted on the left side of the table. A measuring scale is mounted between fixed and sliding jaws. A fixed thread clamp is mounted on the top of the sliding jaw.  The nut is fitted on this fixed thread clamp. This thread clamp is mounted in such a way that it gets tilted when the specimen length increases due to untwisting. The outer end of this fixed thread clamp is connected with a flexible wire. This wire passes over the pulley. A deadweight gets hanged at the other end of this flexible wire. A blackboard is also mounted under the specimen.  






Testing procedure:

The whole testing procedure gets completed in the below steps:

- First of all, the yarn twist direction is identified. 

- Almost 5 metres of the yarn length is removed from the yarn package before mounting the specimen.

 - Now, the distance between fixed and rotating thread clamps is adjusted by moving the sliding jaw in the left direction. 

- The distance between the fixed and rotating clamp is kept at 10 inches.  

- The length of the specimen gets directly proportional to the accuracy of the test result. 

- The yarn specimen is mounted between fixed and rotating thread clamp now. 

- First of all,  one end of the yarn is mounted on the rotating thread clamp.

- Now the other end of the yarn is mounted on the fixed thread clamp.

- The position of the fixed thread clamp is kept at the right angle. 

- A suitable deadweight according to yarn count is hanged one flexible wire. 

- The counter meter is set to zero position now. 

- The spur gear is rotated by hand with the help of the handle according to the twist direction identified early. 

 - The twist is observed with the help of magnifying glass. the blackboard mounted under the specimen helps to increase the clarity of the object being observed.

- When the complete twist gets removed, the technician stops to rotate the spur gear. 

- Now, the final reading of the counter meter is observed and noted. 

- Turns per inch ( T.P.I.) is calculated as below:

T.P.I. = Counter meter reading / specimen test length inches 

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