Monday 10 May 2010

Making Fancy Denim- Amsler Slub, Multicount and Multitwist Yarn



Most of the Cross-Hatch Denim is produced on Amsler Slub or multi-count yarn.

Here are some examples:



Amsler is a swiss fancy-yarn machine manufacturing company. The fabrics produced of the yarn are becoming synonymous with the name of the company

What is Amsler Slub



Amsler yarn can be made on open end or on a ring spinning. 

Mostly amsler slub effect in denim is produced on open end. Thus this is an attachment to open end spinning that allows slub and multi-twist effects at less cost than true ring spun yarn.

The basic problems in producing slub yarn can be enumerated as follows (source):

1. Weak Places in the Yarn: The thick place in the yarn is followed immediately by a thin place, rather than by a simple return to the basic yarn count being spun. This, in turn, creates a weak place in the yarn.  

2. Increase in Basic Yarn twist:

Increased length of the slub leads to the increased twists of the basic yarn. It is necessary to adjust the slub length to avoid basic yarn twist exceeding critical twist.  Twists in every section of the slub yarn are in inversely proportion to the square of the linear density of the corresponding section.


The Principle of Amsler effect goes like this: The Normal yarn is formed from the basic machine speed. There is a microprocessor controlled servomotor that overfeeds with a pre-programmed textile ramp.

In case of ring frame, the servo drive system is connected to the back and middle roller via a special gear box. Only at the time of slub formation the servo motor starts and additional speed is given to the drafting system. Thus the normal yarn formation is not disturbed which results in making a yarn without weak spots. 

In case of open end yarn the principle is the same, ie. excess feed which can be explained with this figure:





Multi-Count Effect



Multi-count yarn, becoming so popular in denim fabrics is produced by a special device. This effect is characterized by having controlled count changes in length ( as short as 2 meters) while maintaining a constant twist level.

Multi-Twist Effect



Multi-twist yarns are those that feature a constant count but have different levels inside yarns. These twist levels create variations in the yarn's dye intake thus creating a special fabric appearance. 

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