1. The STARFISH Approach to Shrinkage & Fabric Engineering

2. Shrinkage - Definition
Shrinkage is the change in dimensions
caused by a relaxation process (e.g. laundering) Lo LS
Original
Dimensions
Lo, Xo Lr
Relaxed Dimensions Lr, Xr
LS% = ( Lo - Lr ) / Lo WS Xr
WS% = ( Xo - Xr ) / Xo Xo

3. Fully Relaxed Dimensions
After several cycles of laundering
the Relaxed Dimensions will become stable
Start
Cycle 1
Cycle 2
Cycle 3
Cycle 4
Cycle 5

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

5. After this procedure, a fabric is said to be in its Reference State.
Reference Dimensions
It is very convenient to know what are the fully relaxed dimensions of each of our fabric qualities.
But, in the real world, nobody has time to discover them
STARFISH standardises on a five-cycle Reference Relaxation Procedure.
Reference State
Dimensions
After this procedure, a fabric is said to be in its Reference State.

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

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

8. Now Consider This
Fabric dimensions are a reflection of stitch density ...
Length
is inversely proportional to the density of Courses ( CPI, C/cm )
Width
is inversely proportional to the density of Wales ( WPI, W/cm )

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

10. Shrinkage LS = 100 . ( Cr - Co ) / Cr WS = 100 . ( Wr - Wo ) / Wr
Shrinkage can be calculated from changes
in the densities of courses and wales
Original Course & Wale
Densities
Co, Wo LS
Reference State Densities Cr, Wr
LS = ( Cr - Co ) / Cr WS
WS = ( Wr - Wo ) / Wr

11. Fabric Width Width (cm) = Needles / Wales per cm
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

12. Therefore Wales/cm (del.) = 0.95 * Wales/cm (ref.)
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.
For example ...
… if the width shrinkage has to be 5%, then
Wales/cm (del.) = * Wales/cm (ref.)

13. Fabric Area Weight Wt = C * W * tex * loop length
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

14. By the way ... For a fixed area weight (e.g. customer specification)
and a given basic fabric quality ...
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.
In other words, there is a particular value for the course density that goes together with certain values of weight, width and shrinkage.

15. So, 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.

16. Engineering 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.
This knowledge is built into the STARFISH software

17. The faster, cheaper, more reliable way of doing product development.
STARFISH Version 6.5
The faster, cheaper, more reliable
way of doing product development.