Tuesday, June 25, 2019

WOVEN VELVET FABRIC, TYPES OF VELVET FABRICS, METHOD OF WEAVING OF VELVET FABRICS, USES, DEFECTS AND REMEDIES

WOVEN VELVET FABRICS, TYPE OF VELVET FABRICS, METHOD OF WEAVING, USES OF VELVET FABRICS

VELVET FABRIC:

The velvet fabrics have cut piles on the one side of fabric surface.  There are two types of velvet fabrics manufactured.  One is known as warp pile fabric and another is called weft pile fabric.  Cotton, acrylic, viscose filament, and polyester yarn are widely used to manufacture velvet fabrics.  Either multi- plies spun yarn or multi – filaments viscose yarn is used to make piles. The velvet fabrics are widely used to make garments, jackets, purses, car sheeting,  ( automobile industry), quilts, pillow covers etc. 

TYPES OF WOVEN VELVET FABRICS:

There are two types of woven velvet fabrics manufactured:

1- Warp pile velvet

2- Weft pile velvet

1- WARP PILE VELVET:

In this velvet fabric,  the warp yarn makes piles on the fabric surface.  Two series of warp and one series of weft are use to make this pile fabric. The one warp series is known as ground warp and other series is known as pile warp. Since pile side is the face of the fabric,  so that superior quality pile warp yarn is used to make warp pile velvet. 

THE METHOD OF WARP PILE VELVET WEAVING:

There are two methods used to manufacture warp pile velvet:

SERRATED WIRES INSERTION METHOD:

In this principle,  the pile formation takes place with the help of serrated wires.  Single fabric weaves at a time in this method. One ground warp and one pile warp are used in this method. The ground warp and weft make plain fabric.  The the serrated wires are inserted in the shed according to design and peg plan. When the pile warp passes over the serrated wire,  it makes loops of pile warp. The serrated wires are eliminated after weaving.  The loops of pile warp get cut during elimination of serrated wires.  Thus cut piles of warp yarn are formed on the fabric surface. There are double let- off systems required in the loom to weave the fabric. The pile density can be increased by increasing picks per inch.

The productivity of this system is very low. There are required different sizes of serrated wire to weave the fabric with different pile heights.



FACE TO FACE PRINCIPLES METHOD:

In this method of velvet manufacturing,  two fabric are woven simultaneously.  The faces of the both fabric opposed to each other. The two layers of the fabric are separated with the help of cutting knife continuously during weaving.  There are two ground warp beams are used to make the velvet. One ground beam is used to make top fabric and other ground warp beam is used to make bottom fabric. Pile warp is used commonly for both fabrics.

  
The face to face velvet is woven by using following methods:

FACE TO FACE VELVET WEAVING BY USING SINGLE SHUTTLE PRINCIPLE:

In this method, single ground warp is used for top and bottom fabric both. Pile warp beam is used commonly for both fabrics. It is woven on the loom equipped with double let- off and normal shedding mechanism. Minimum six heald shafts are required to make the velvet fabric. Since we know that velvet fabrics are heavy weight fabric. It requires a special take – up rollers. There are two take – rollers having strong spikes on their surface are used in the loom.  Batching motion is used to wind the cloth on clothe rollers.

A cutting motion equipped with self sharpening mechanism is used to separate the two layers of the fabric.
In single shuttle velvet weaving process,  the productivity is low.

FACE TO FACE VELVET WEAVING BY USING DOUBLE SHUTTLE PRINCIPLE:

In this weaving mechanism, special type of dobby mechanism is used. The warp ends making ground fabric raise and lowered in two positions. Top fabric ground ends move from middle to top position and top to middle position.  The bottom fabric ground ends move from bottom to middle and middle to bottom position. The lifting mechanism of dobby is designed in such a way that pile ends can move in three positions ( top, middle, and bottom).  Thus two sheds are formed at a time.  The picks are inserted in both sheds individually at a time with the help of two shuttles or rapiers ( in Shuttleless weaving ). The machine is equipped with self sharpening pile cutting mechanism and double take – up rollers having strong spikes on their surface. Batching rollers are used to wind the cloth on the cloth winding rollers.

In double shuttle velvet weaving process, the productivity is very high because double weft insertion.

TYPES OF PILES:





DEFECTS OF WARP PILE VELVET FABRIC:

Since the velvet fabric is entirely different from flat woven fabric,  so that the fabric defect in velvet fabric appear in different form.  The main defects of the velvet fabric are given below.

1- missing pile end: 

if the pile end get missing in the velvet fabric,  it appears clearly on the fabric surface. The ground fabric starts to look due to missing pile in the form of warp wise deep bar.  If the pile end gets missed,  it appears in the both fabrics ( top and bottom fabric) . This defect is mendable if the pile end is missed for short length.

2- Missing ground end:

If the ground end gets missed, it appears in the form of piles freying on the face side. This defect appears in one fabric. This is un repairable defect.

3- Missing pick:

If the pick gets missed in any one fabric layer,  the piles do not form over that place,  a deep weft bar appears in both fabric ( top and bottom fabric).  It is unrepairable defect.

4- Rough cutting:

the layer separation of velvet is always a very big issue.  The cutting blade gets sharpened after insertion of every alternate pick.  Due to improper sharpening of cutting blade causes rough cutting of velvet fabric.  The piles begin to come out from the fabric.  Uneven fabric appearance results due to rough cutting of velvet fabric.  If rough cutting appears on the fabric surface,  both the fabric get rejected.

5- Blade marks:

If there is excessive clearance between knife carriage and knife carriage rail it causes partial or full blade mark in the velvet fabric.  The pile height for one pick is either increased or decread.  This defect appears as weft bar partially or full fabric width. This is unrepairable defect. This defect appears in both fabrics ( top and bottom).

6- Low pile height bands:

 in this kind of defect,  the pile height for a very short length is decreased suddenly.  It appears like weft wise band in the fabric.  It generates if the pile warp tension is increases suddenly for a very short period during weaving.  It also generates if the tension if either bottom ground beam or top ground beam decreases suddenly for a very short period during weaving.  This is unrepairable defect.

7- Pile warp bands:

this defect results if the warp tension of pile warp or any ground warp does not maintain regularly.  The low and high weft wise bands generate in both the fabrics.  The fabric gets rejected.

8- Height difference between left and right pile.:

This kind of defect appears due to improper setting of top and bottom jaws.  This defect appears in both fabrics ( top and bottom).

FINISHING OF VELVET FABRIC:

The grey velvet fabric has a lot of fibre fluff in it. The the many fibres also appears on the fabric surface.  These fibres makes the fabric surface uneven.  The seen ( lustre)  of the fabric also does not come out clearly.  The cut pile fibres do not open fully.  These unopened fibres of pile yarn affects the richness of the fabric surface.  The grey velvet fabric is passed through a velvet finishing machine. Following actions take place in the finishing machine:

Beating zone: 

First of all , the fabric passes over the beating roller,  the dust and fluff eliminate in this beating zone. 

Raising zone: 

The face side ( pile side)  of the fabric comes into the contact of a raising roller. The rotating raising roller helps to open the twist of pile yarn. 

Shearing zone: 

This is the last acting zone. This zone consists of one rotating spiral blade at high speed. One fixed blade is also mounted over spiral blade.  The clearance between both blades is kept minimum. When the fabric passes into this zone,  the extra fibres on the face of the fabric get cut evenly.  The surface gets much clean and clear.  The seen( lustre)  of the fabric come out clearly.  The richness of the fabric also improved. 

The W- pile and V-pile on alternate pick show fast pile structure.  The regular V-pile and U- pile show poor fastness of pile structure.  These kind of structure needs a special treatment to improve the fastness of the structure. A coating of latax rubber is applied on the back of the fabric.  This treatment helps to improve the fastness of pile structure in the fabric. 

                                THE END







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