Which are the major dyeing faults and what are their remedies?

Dyeing Faults and Remedies

1.Snagging:

Definition:-

·       Snagging appears on the knitted fabric surface, as a pulled up yarn float, showing up in a form of a large loop.

Causes:-

·       Cause by the pulling or the plucking of yarn from the surface, by the sharp objects.

Remedies:-

·       Inspect & rectify the fabric contact points on all machines ( Soft flow dyeing , Tumble dryer  & Centrifuge etc). On which Snagging is making.

2. Bowing:

Definition:-

·       Bowing appears as, rows of courses or yarn dyed stripes, forming a curb shape as bow, along the fabric width.

Causes:-

·       Uneven distribution of tensions across the fabric width while dyeing or finishing the fabric.

Remedies:-

·       Bowing can be corrected, by reprocessing of the fabric, by feeding it from the opposite end.

·       A special machine (MAHLO) is also available for correcting the bowing in the knitted fabrics, which set in the stenter machines.

3. Curling the edge of single jersey / Lycra single jersey fabric:

Definition:-

·       When the single jersey/ lycra single jersey fabrics laying on the table the both side salvage may be curling (rope).

Causes:-

·       Dimensional instability of the single jersey knitted fabrics.

·       The face side of the fabric has loops; whereas the back side has only yarn floats, so there is an imbalance between the face & back side of the fabric.

Remedies:-

·       Gumming of both edges of the single jersey fabrics, while stentering can be control the curling.

4.  Measurement Problems:-

Definition:-

a).The measurements of the garments totally changed after a few hours of relaxation or after the first wash. The sleeve length or body length /body front or back length may be variation due to insufficient relaxation/shrinkage / steam iron or part mistake.

Causes:-

a).Shrinkage caused due to inadequate relaxation of the knitted fabrics, before cutting.

b).Mixing of the garments parts cut from different layers or different rolls.

Remedies:-

a).Let the fabrics relax for 6^th-12^th hours in the roll open relaxed condition, before cutting. Especially LYCRA fabrics.

b).Use a trolley for laying the fabrics on the table to facilitate a tension free laying.

c).Ensure the numbering or gassetsystem, so that we prevent the lay or body mixed up.        

5. Folding marks:

Definition:

·       Folding marks appear as distinct pressure marks, along the length of the fabric.

Causes:-

·       High pressure of the fabric take down rollers of the knitting machine, on grey fabric is one of the main causes.

·       Too much pressure of the feeding rolls of the calendar & compactor is the primary causes folding marks in the knitting fabric.

Remedies:-

·       Adjust the gap between two rolls, as per thickness of the fabrics.(mainly in Pique, S/J, etc.).

·       Gap between two rolls of the compactor/calendar should be just enough, to let the rolls remove, the wrinkles in the fabric, but put no pressure on the fabric, especially in case of PIQUE & SINGLE JERSEY fabric.

6.   GSM Variation:-

Definition:

·       The fabric will appear to have a visible variation in density, from roll to roll or within the same roll of the same dye lot.

Causes:-

·     Roll to roll variation in the process parameters, of the fabric, like over feed &width wise stretching of the dyed fabric, on the stenter, compactor or calendar machines.

·       Roll to roll variation in the fabric stitch length.

Remedies:-

·       Make sure that all the rolls in a  lot, are processed under the same process parameters.

·       The knitting machine setting, like; the quality pulley diameter etc. should never be disturbed.

 7.  Fabric width Variation:-

Definition:

·       Different rolls of the same fabric lot, having difference in the finished width of the fabric.

Causes:-

·       Grey fabric of the same lot, knitted on different makes of knitting machines, having varying number of Needles in the cylinder.

·       Roll to roll difference, in the dyed fabric stretched width, while feeding the fabric on the stenter, compactor or calendar.

·       9The whole lot of grey fabric should be knitted on the same make of knitting machines.

·       For same gauge & diameter of the knitting machines, there can be a difference as high as 40 needles  from one make to other make of the machine, these difference of up to 2”-3” Finished DIA( + or –) of the fabrics.

·       During stenter&finishing, the stretched width of the fabrics should be remaining constant.

8. Stains:

Definition:-

·       Stains appear as a spots or patches, of grease, oil or dyes of different color, in a neat & clean finished fabric’s surface. It is a common defect.

Causes:-

·       Dyeing machine do not cleaned thoroughly, after dyeing a lot.

·       Grease, oil & rust stains from unguarded moving machine’s parts like; Gears, Shafts, Driving pulls& Trolley wheels, and irons plates.

·       During transportation, fabric touched in the floor or soiled/dirty places.

·       Handling of the fabric, with dirty hands or stepping into the stored fabric with dirty feet or shoes on.

Remedies:

·       After dyeing the machine should be wash & clean properly.

·       Follow the dyeing cycle of LIGHT-MEDIUM- DARK shades & then reverse the cycle, while dyeing the fabrics.

·       All the lubricated machine parts should be protected, with safety guards.

·       Make sure that the fabrics is neatly packed or covered by clean polythene, while storeing.

·       Handle the fabric with carefully, with clean hands, do not step on the fabric.

9.  High Shrinkage:

 Definition:-

·       The original intended measurements of the garments go , haywire, during storage or after a very first wash.

Causes:-

·       High stresses & strains exerted on the fabric, during knitting, dyeing & processing and the fabric not being allowed to relax properly.

·       High shrinkage is primarily due to the high tension, during knitting, dyeing and the finishing processes.

Remedies:

·       Keep the grey fabric in loose plated form, immediately after the roll cut.

·       Store the finished fabric also in the plated form not roll form.

·       Before cut the fabric must be relax properly.

·       Give maximum overfeed to the fabric, during processing, on the Stenter, Compactor the Calendaring machines.

10. Surface Hairiness & Piling:-

Definition:-

·       Surface hairiness appears in the form of excess superfluous fibers, on the surface of the knitted fabrics, which have either been reprocessed, or tumble dried.

·       Piling appears as small fiber balls formed on the fabric surface, due to the entanglement of the loose surface fibers.

·       Factor such as, the fiber staple length, low T.P.M. & fabric construction (With long yarn floats) etc. also contribute to piling.

Causes:- 

·       Abrasion due to the contract with rough surfaces.

·       Excessive surface hairiness caused, due to the abrasive tumbling action (Fabric friction in the tumble dryer).

·       Rough dyeing process and abrasive machine surface (Soft flow machine tubes, Tumble dryer drum etc).

·       Reprocessing of the fabric is, also a major cause of piling.

Remedies:-

·       Avoid using Tumble dryer.

·       Control shrinkage by maximum fabric relaxation& over feed in the processing.

·       Regularly inspect the fabric contact points on all the machines, for any rough and sharp surface. And rectify.

·       Avoid repeated reprocessing of the fabric.

Use anti piling agent for the fabrics, prone to piling.

 Collected  By: Md. Tarikul Islam

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