Fabric Bowing & Skewing
Bowing & Skewing are defects which are created when there is a distortion in weft laid across the whole with of the fabric.
Bowing & Skewing are defects which are created when there is a distortion in weft laid across the whole with of the fabric. Both need to taken care and handled properly during weaving and finishing to avoid wastage at garmenting stage.
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 selvedge and lie in a wave or arc across the width of the fabric.
Bowing can be called as a 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 the final finished fabric.
Picks are inserted at an angle of 90o during beating action so Warp and Weft should be at a perpendicular angle always. But it never happens. Post beating (fell of cloth), fabric goes through a lot of processes and formation of bowing happens.
Bowing formation at the weaving stage
Nowadays fabric are being produced on high-speed shuttle looms, where fabric selvedge at both ends is being held by temples having sharp pins impregnated in the fabric; Which in turn avoid fabric to roll back post beating action due to let off motion force. During take up action when the fabric is being pulled then application of force is more at the center of the fabric, and less at selvedge due to temple hold. And bowing of 1” to 1.5” is being generated in the fabric at both selvedges 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) fewer chances of bowing will be there.
- Finer the yarn count (Indirect system) more chances of bowing and coarser the yarn count then fewer 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 the Processing stage
Here are the key reasons which are responsible for fabric bowing formation during fabric processing.
- Fabrics in processing mill go through a lot of processes like singing, desizing, bleaching, mercerizing, dyeing, sanforising and stentering. There can be other processes like peaching etc. During all these processes fabric has to pass through set of rollers many times and every time when fabric passes through a nip of rollers there is a chance of bowing formation if there is any speed variation in between 2 sets of rollers.
- Another important reason for bowing generation is machine operator negligence during fabric stitching. At the time of fabric stitching to make a batch, if proper care and attention is being given by operator then bowing can be minimized. At any given point of time if a 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.
- Stenter machine is key machine in fabric processing and acts an important role in fabric bowing. If the fabric is not being fed properly in stenter machine then chances of fabric bowing generation will be there.
Measurement of Bowing
As per picture given below, we can see distortion at the center of fabric marked as ‘b’ and the total fabric width is being as ‘d’
Bowing can be calculated as below
Skewing is a common fabric defect in woven fabrications where weft or filling yarns are distorted means pattern on one side of the 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 the 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) fewer chances of skewing will be there.
- Finer the yarn count (Indirect system) more chances of skewing and coarser the yarn count then fewer chances of skewing will be there.
Measurement of Skewing
As per the picture given below, we can see distortion at the center of fabric marked as ‘b’ and the total fabric width is being as ‘d’.
Skewing can be calculated as below