Dimensional stability

Textile Knit fabrics Finishing

1. MAA Garment & TextilesMAA Garment & Textiles
(Kebire Enterprises PLC)

2. Mohammad Mizanur Rahman.
Manager (Finishing Expert)
MAA Garment & Textiles
Presented By

3. Understanding Understanding
the Shrinkage & Fabric the Shrinkage & Fabric
EngineeringEngineering

4. Shrinkage - DefinitionShrinkage - Definition
Original
Dimensions
Lb, Wb
LS% = 100 . ( Lb - La ) / Lb
WS% = 100 . ( Wb - Wa ) / Wb
Shrinkage is the change in dimensions (width and length)
caused by a relaxation process (e.g. laundering)
LS
WS
Wb
LbLa
Wa
Relaxed
Dimensions
La, Wa

5. Fully Relaxed Dimensions Fully Relaxed Dimensions
= Refference State= Refference State
After several cycles of laundering
the Relaxed Dimensions will become stable
Cycle 1
Cycle 4
Cycle 3
Cycle 2
Cycle 5
Start
Unknown Shrinkage
Length X Width
15% X 15%
18% X 17%
19% X 18%
19.5% X 18.5%
19.7% X 18.8%

6. Fully Relaxed DimensionsFully Relaxed Dimensions
These are the
Fully Relaxed Dimensions
After several cycles of laundering
the Relaxed Dimensions will become stable
Fully
Relaxed
Dimensions
Practically speaking,
no further shrinkage
is possible
Some fabrics may require ten
or more cycles to relax fully,
though most of the shrinkage
occurs in the first five cycles.

7. Reference DimensionsReference Dimensions
But, in the real world, nobody
has time to discover them
It is very convenient to know what are the fully relaxed
dimensions of each of our fabric qualities.
Reference State
Dimensions
But It is a must to find this
out, either in grey or after the
Dryer stages.
After this procedure, a
fabric is said to be in its
Reference State. And
very useful to get the
correct target.

8. Shrinkage - VariationShrinkage - Variation
But the
Reference Dimensions
would still be the same
(within practical limits).
If I took the original piece of fabric and stretched it
in length and width ...
Because (practically)
no further shrinkage
is possible at this stage.
Reference
State
Dimensions
do not change
LS
WS
... it would shrink more because
the Original Dimensions are greater.

9. In GeneralIn General
Fabric Dimensions, as delivered at the end of the
finishing line, can vary over quite a wide range ...
the Reference Dimensions
will always be the same.
But, for a given basic
fabric quality and wet
processing treatment ...
... depending on the skill of the finisher and the targets
he is trying to hit.
Width Wise Setting

10. Now Consider ThisNow Consider This
Fabric dimensions are a reflection of stitch density ...
 Length
is inversely proportional to the
density of Courses ( CPI (courses per inch),
C/cm (courses per centimeter)
 Width
is inversely proportional to the
density of Wales ( WPI (wales per inch,
W/cm (wales per centimeter)

11. It Follows ThatIt Follows That
Fabric Width, Weight, and Shrinkage
Can be calculated from
Course and Wale Densities
For example ...

12. ShrinkageShrinkage
LS = 100 . ( Ca - Cb ) / Ca
WS = 100 . ( Wa - Wb ) / Wa
Shrinkage can be calculated from changes
in the densities of courses and wales
Reference State
Densities
Ca, Wa
LS
WS
Original Course & Wale
Densities
Cb, Wb

13. Fabric WidthFabric Width
There is a fixed number of total wales,
depending on the knitting machine
that was used to make the fabric.
Therefore, the width is determined by
the wale density ...
Width (cm) = Needles / Wales per cm

14. ThereforeTherefore
If I know what is the wale density in the
Reference State fabric ...
… I can easily calculate what must be the
wale density in the As-delivered fabric
for any given shrinkage value.
Wales/cm (del.) = 0.95 * Wales/cm (ref.)
For example ...
… if the width shrinkage has to be 5%, then

15. Fabric Area WeightFabric Area Weight
Can also be calculated from Courses and Wales...
Area weight is the number of loops per unit
area multiplied by the weight of each loop
Wt = C * W * tex * loop length
number of loops weight per loop
tex is yarn weight per unit length

16. By the way ...By the way ...
For a fixed area weight (e.g. customer specification)
and a given basic fabric quality ...
In other words, there is a particular value for the course
density that goes together with certain values of weight,
width and shrinkage.
 If the fabric width is fixed (as it usually is)
then the fabric length must also be fixed.
 Therefore the number of Courses per cm
(and hence the length shrinkage) is also fixed.

17. So, It Comes Down To ThisSo, It Comes Down To This
If I know what are the course and wale densities
in the Reference State for a particular fabric quality (after
dyeing and finishing) then ...
… I can easily calculate the course and wale densities
that must be in the As-delivered fabric in order to guarantee
a certain level of shrinkage ...
… and I can calculate the corresponding width and area
weight of the delivered fabric.

18. Engineering of FabricsEngineering of Fabrics
In order to be able to guarantee specific values of
weight, width and shrinkage in the fabrics that I
deliver to my customers ...
… I need to be in possession of a detailed
knowledge of the course and wale densities
in the Reference State of any fabric
that I am likely to be asked to supply.

19. Knitting Preparation Dyeing
Dewatering Dryer
Slitting
Stenter
Open Compactor
Stenter
Hydro
Extractor
SuedingBrushing
Flow Process of Fabric KnitsFlow Process of Fabric Knits

20. The faster, cheaper, more reliable
way of doing product development
Is to do the Reference State Test And Use
its data.
Thank YouThank You