Weft Calculation
During weft calculation in weaving, the following formula will be found useful for determining various particulars required in practice. They have all been derived from the fundamental formula,
Count = Number of hanks per lb.
1. Width of warp in reed in inches,
Regain% of weft + 100
= ……………………………………. × Cloth width in inches
100
2. Width of warp in reed in cms,
Regain% of weft + 100
= …………………………….. × cloth width in cms
100
3. Total length of weft in yds,
= Total number of picks × Length of weft in reed in yds.
Or,
= Length of cloth in yds × picks per inch in cloth × Reed width in inches
4. Total length of weft in metres,
Total number of picks × length of weft in reed in cms
= …………………………………………………...........…..
100
= Total number of picks × length of weft in reed in metres
= Length of cloth in metres × picks per cm in cloth × reed width in cms
5. Total length of weft in km,
Length of cloth in metres × picks per cm in cloth × reed width in cms
= ……………………………………………………………………………………
1000
6. Total length of weft in hanks,
Length of cloth in yds × picks per inch in cloth × Reed width in inches
= ………………………………………………………………………………………..
840
7. Weight of weft in grms,
= Total length of weft in km × count of weft yarn in tex
= Count of weft yarn in tex × length of cloth in km × picks per cm in cloth × reed width in cms
Count of weft yarn in tex × length of cloth in metre × picks per cm in cloth × reed width in cm
= ……………………………………………………………......................................…….......……
1000
8. Weight of weft in lbs,
Total length of weft in hanks
= …………………………………….
Count of weft
Or,
Length of cloth in yds × picks per inch in cloth × Reed width in inches
= ………………………………………………………………………………………..
840 × Count of weft
9. Weight of weft in kg;
Count of weft yarn in tex × length of cloth in metre × picks per cm in cloth × reed width in cm
= …………………………………………………………………………..………………….......……
1000 × 1000
10. Count of weft,
Total length of weft in hanks
= …………………………………….
Weight of weft in lbs
Or,
Length of cloth in yds × picks per inch in cloth × Reed width in inches
= ………………………………………………………………………………………..
840 × Weight of weft in lbs
11. Count of weft in tex,
Weight of weft yarn in grms
= …………………………………………
Length of weft yarn in km
Weight of weft yarn in grms × 1000
= ……………………………………………………………............…………
Length of cloth in metres × picks per cm in cloth × reed width in cm
Example 01:
Calculate the count of the weft of a piece of cloth 20 metres long and has 25 picks per cm. The width of the cloth is 80 cms and the weft regain is 10%. The weight of the weft is 2.16 kg.
Solution:
Reed width in cms,
Regain% of weft + 100
= …………………...............× cloth width
100
100 + 8
= ……….. × 80
100
108 × 80
= ……………
100
= 86.4 cms
Now,
Count of weft,
Weight of weft yarn in grms × 1000
= ……………………………………………………….............………………
Length of cloth in metres × picks per cm in cloth × reed width in cm
2.16 × 1000 ×1000
= …………………………….
20 × 25 × 86.4
= 50 tex
So, the count of the weft of a piece of cloth is 50 tex. (ANS)
Example 02:
A cloth 52.5 inches wide on the reed is 42 yds long and contains 60 picks per inch. If the weight of weft in the cloth is 3.5 lbs. what is the count of the yarn?
Solution:
Count of weft,
Length of cloth in yds × picks per inch in cloth × Reed width in inches
= ………………………………………………………………………………………..
840 × Weight of weft in lbs
42 × 60 × 52.5
= ………………..
840 × 3.5
= 45s cotton.
So, Count of weft yarn is 45s cotton. (ANS)
