Post on 01-Nov-2014
description
....DYEING , PRINTING AND
FINISHING DEFECTS AND REMEDIES….
The reasons like water, fiber sources & processing conditions is responsible for defects during wet processing. However, in order to overcome/ minimize the processing related problems it is essential to first understand the Symptoms (problems), Diagnose (ascertain the probable cause) & Cure (adopting remedial measure).
Some defects of various stages are disscussed below:
Causes Of Dyeing Defects
Due to Material:– Material having dead fibers or other defective fibers.
– Left over of Chemicals after scouring, bleaching etc.
– Material not properly singed, desized.
– Material not properly mercerized.
– Absorbency of the fabric not proper.
– Sticking of insoluble material on the fibers.
– Impurities are not removed properly.
– Uneven heat treatment.
Causes Of Dyeing Defects
Due to Water Quality:– More Hardness of water
– Water has metal ions such as iron.
– pH of water not proper
– Water having more chlorine
Due to Improper Dye Solution:– Improper weight ratio of colors, material and chemicals.
– Improper material to water ratio
– Improper filtering of concentrated colors.
Dyeing Defects
Bleeding
• It’s a loss of color when the dyed fabric is wetted or emerged in water.
• The water here, becomes colored and may cause discoloration of other fabrics.
• This is usually due to either improper dye selection or poor dye fastness.
• It is the rubbing off of the color.
• It may rub onto another fabric.
• This may be due to inadequate scoring subsequent to dyeing.
Crocking
Shade Bar
• It is a horizontal band of a different hue running across the fabric.
• It may be caused by a change of filling bobbin in the loom or a loom stop and start up
Hole in sulfur dyed fabric
• Caused due to tendering which
takes place because sulphur is
converted into sulphuric acid
after oxidation which is harmful
for the cellulosic fibers.
• This is a major defect. The defect
occurred after washing the garment.
Off Shade
• It refers to color that doesn't exactly match the standard or the prepared sample.
• This may be due to faulty dye foundation or application or may be due to variation in dye lot.
Uneven Dyeing
Batch to batch Shade Variation
Patchy Dyeing Effect
Roll to Roll Variation
Crease Mark
Printing Defects
Flushing/Wicking
• Caused due to Low viscosity of print paste.
• It occurs when the printed area
bleeds out into the unprinted
area. The result is a ‘haloing’ or
shadowing effect around the
outline of the pattern design.
Bleeding
• Caused due to Low viscosity of
print paste
• It is major defect as it happens
throughout the fabric unless
the viscosity is corrected.
Misfits
• A misfit is a print defect caused by improper alignment of the
screens. Also known as “out of registration, misfits leave
unprinted areas in the design.
• For example, a green leaf may overlap its black outline or
print over another color.
Banding
• Defect created by the print head’s movement over the substrate.
• Use of scanning print head, or a print head that moves back and forth
across the substrate in straight line placing drops of ink at precise
locations along the line.
• If the head is not properly aligned, or if the substrate advances
unevenly, the result is a slight horizontal “band” or line of unprinted
area.
Unwanted pigmentmarking on fabric
• Caused due to screen has holes
in it that should have been
covered. This could be because
of ageing of the screen and
eventual damage or just
improper exposure to light.
Crack or miss alignment in transfer printed fabric.
• Incomplete transfer of design
from paper to fabric on transfer
printing due to removal of
transfer of paper while the
fabric was still hot.
Finishing Defects
FABRIC FINISHING
• A series of processing operations applied to
gray fabrics to enhance their appearance and
hand, properties and possible applications.
• Play a fundamental role for the commercial
excellence of the results of textiles
FABRIC FINISHING
• The most simple form of finishing is the ironing or pressing on the fabric.
• In finishing , the fabric is subjected to mechanical and chemical treatment in which its quality and appearance are improved and its commercial value enhanced.
• Physical finishing techniques(dry finishing processes) or chemical finishing methods(wet finishing) are used.
FABRIC FINISHING
• Functional finish:
– Wearability, Hand, Mechanical resistance,
Easy care, Wettability, Washability,
Deformability, Anti bacterial, Anti fungal,
Soil-proof and Fire-proof ability
• Aesthetic finishes:
– Aesthetic looks
• Oily stains with dust adhered to
surface which makes the stains
more prominent and difficult to
remove, due to contact with oil
or grease covered exposed
machine parts, careless handling
could be another cause.
Unwanted marks on fabric.
• Caused due to
– chemical spillage on fabric.
– Localized excess bleaching.
– Localized excess enzyme wash.
• Can be result into weakening of
the fabric.
Decolorized patch on fabric
• Holes along selvage caused by pins holding fabric while it
processes through tenter frame.
• Major defect if pin holes extend into body of fabric far
enough to be visible in the finished product.
Pin Holes
• Results from uneven wetting out on sanforize.
• usually caused by defective spray heads.
• Fabric will appear wavy or puckering when spread on cutting
table.
• Difficult to detect during inspection on inspection machine
with fabric under roller tension.
Sanforize Pucker
Bowing
• Usually caused by finishing.
• Woven filling yarns lie in an arc across fabric width; in knits
the course lines lie an arc across width of goods.
• Establish standards of acceptance. Critical on stripes or
patterns; not as critical on solid color fabrics.
Pilling
• Pilling is a common fabric defect occurring on knitted and woven fabrics.
• In producing a yarn, long fibers tightly-twisted produce a serviceable yarn. When short stable fibers are mixed into the yarn the result is a yarn that will not hold together. The short staple fibers will separate from the yarn and curl up in a ball, forming what is referred to as a pill.
• Pilling is accentuated by the friction of normal wear, washing and routine dry cleaning.
Water Spots
• Usually caused by wet fabric being allowed to remain too long
before drying; color migrates leaving blotchy spots.
Selvage Torn
• Usually caused by excessive tension while processing through tenter frames.
Cuts or Nicks
• Caused by indifferent handling of scissors. snips ormechanical trimmers.
Soil
Caused by oil, grease or dirt. Often times originating from a dirty work area or machinery not properly cleaned