Bowing and Skewing are defects which are created when there is a distortion in weft laid across the whole with of the fabric. These faults are very critical for fabric. Every textile engineer should keep clear concept about bowing and skewing in fabric (see in below diagram). In this article I will discuss bowing and skewing formation in fabric details.
Bowing Defects of Fabric:
Bow or bowing is a common fabric defect in woven fabrications where weft or filling yarns are displaced from a line which needs to be perpendicular to the selvage and lie in a wave or arc across the width of the fabric.
Bowing can be called as defect but in case of some woven patterns (2/2 Twills), bowing is being introduced (During fabric processing) in fabric to avoid residual bowing in final finished fabric.
Picks are inserted at an angle of 90o during beating action so Warp and Weft should be at perpendicular angle always. But it never happens. Post beating (fell of cloth), fabric goes through lot of processes and formation of bowing happens.
Bowing formation at weaving stage:
Now a days fabric are being produced on high speed shuttle looms, where fabric selvedge at both end is being held by temples having sharp pins impregnated in fabric; Which in turn avoid fabric to roll back post beating action due to let off motion force. During take up action when fabric is being pulled then application of force is more at center of fabric, and less at selvedge due to temple hold. And bowing of 1” to 1.5” is being generated in fabric at both selvedge ends. This is called as Residual Bowing at Greige fabric.
Needless to say,
- Lighter the fabric in weight (gsm) more chances of bowing and heavier the fabric in weight (gsm) less chances of bowing will be there.
- Finer the yarn count (Indirect system) more chances of bowing and coarser the yarn count then less chances of bowing will be there.
Above mentioned bowing can be corrected during fabric processing and doesn’t impact fabric geometry and its dimensional stability.
Bowing formation at Processing stage:
Here are the key reasons which are responsible for fabric bowing formation during fabric processing.
a) Fabrics in processing mill goes through lot of processes like singing, desizing, bleaching, mercerizing, dyeing, sanforising and stentering. There can be other process like peaching etc. During all these processes fabric has to pass through set of rollers many times and every time when fabric pass through a nip of rollers there is a chance of bowing formation if there is any speed variation in between 2 set of rollers.
b) Other important reason of bowing generation is machine operator negligence during fabric stitching. At the time of fabric stitching to make batch, if proper care and attention is being given by operator then bowing can be minimized. At any given point of time if roll of greige fabric is being stitched with another greige roll at an angle then it’s a start of bowing and this will increase in further processing.
c) Stenter machine is key machine in fabric processing and act important role in fabric bowing. If fabric is not being fed properly in stenter machine then chances of fabric bowing generation will be there.
Skewing Defects of Fabric:
Skew or skewing is a common fabric defect in woven fabrications where weft or filling yarns are distorted means pattern on one side of fabric is ahead or behind the pattern on the opposite side.
This is usually caused in fabric weaving or processing when both fabric edge will be pushed by roller with different force. So due to difference in force at each edge cause the movement of weft pattern.
Needless to say,
- Lighter the fabric in weight (gsm) more chances of skewing and heavier the fabric in weight (gsm) less chances of skewing will be there.
- Finer the yarn count (Indirect system) more chances of skewing and coarser the yarn count then less chances of skewing will be there.
Author of this Article:
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.