Most suitable count for knitting machines
As a thumb rule knitting experts
prefer to use such knitting machine whose gauges is near to count of yarn
(English count) i.e. for 20-gauge machines most suitable yarn count is 20s.
This rule is has certain limitations, like, for 28-gauge yarn of 26s to 30s is
most suitable. But for very fine counts this rule is not applicable and also
machines have maximum gauge 32. Normally fine counts are not used as such
rather they are make double, like count 60s double, which means that net count
is near to 30s. And this 60 double count is suitable for 30-gauge machine.
To solve this problem some
authors have suggested following formulas.
For single Knitting Machine
Suitable count = G*G/18
For Double knitting machine
Suitable count= G*G/8.4
Where G is gauge of knitting
machine
Some knitting machine
manufacturers suggest a range of yarn count for their machine.
There is another way to solve
this problem and that is to take help from old record. Every firm is producing
many types of fabrics and on the basis of experience they develop a database
for ready reference.
One can get a ready reference
from the table to produce fabric of certain grammage. We are also giving
expected width of fabric after wet processing.
This table can provide just a
reference. Knitters have to decide by themselves after doing a trial
production, since there are many more factors, which can affect yarn and gauge
selection process.
Knitting
Machine Parameters
Every knitting machine is made to
fulfil certain demands of the customer.
There are number of
characteristics of machine which are intimated by the machine manufacturers
while delivering the machine to customers/users.
It is helpful for the user to be
well aware about these parameters. Furthermore machine specifications are given
in different unit. We will explain these parameters and will also give the
conversion factors to convert parameters from one system to other.
Machine Gauge
As per Oxford Dictionary the word
“gauge” is a noun and as well as verb. It is used to measure level of any thing
or for an instrument to measure width, length or height of any thing.
In knitting it is used to express
the number of needle in a unit length of the needle bed. This needle bed may
flat or circular.
In double knit circular machine
it is used for cylinder and as well as dial. Generally gauge is defined as
number of needles per inch.
According to German standard DIN
60917 (Iyer et al1995) alphabet “E “ is used to denote knitting machine
gauge.
E = Number of needles
1 inch (25.4 mm)
Machine Pitch
As per German DIN 62125 (Iyer et
al1995) the notation “gauge” is to be avoided in the future. Rather they prefer
to use notation “pitch” for comparison purpose.
Machine Pitch means the distance
between the centres of two neighbouring needles. It is denoted with small “t”.
It is given in mm.
Knitting Machine Production calculation
Before explaining the method to
calculate the nominal production capacity of the knitting machine it is
imperative to be well aware of count and denier system and one should also be
familiar with the conversion factors.
Yarn is sold and purchased in the
form of cones and bags. Cones and bags have certain weights.
Still in the international market
yarn is sold in pounds not in kilograms. Bags are of 100 pounds, which is equal
to 45.3697 kgs.
Previously there were 40 cones in
a bag but now there are bags available of 25 cones. In other words cones are of
2.5 pounds and four pounds.
Nominal Production of knitting machines
One very simple way to calculate
knitting machine production by weighing the total production of one hour or one
shift or one day.
The practical way calculating
production of a machine is as follows. In this method following information for
production calculation are required:
- Machine
Guage and Dia
- RPM
Knitting Machine
- Yarn
Count
- Stitch
Length
From these figures we
can calculate the length of yarn being used by the machine in one hour and then
by converting this length into weight with the help of count given we can
calculate the quantity of yarn being consumed by machine in one hour. This
would be the optimum production of the machine. This optimum production can be
converted into nominal production by multiplying it with efficiency. In the following pages we will explain this
with few examples.
In the following pages we will
explain the method to calculate nominal production capacity of knitting
machine. It is commonly believed that we can run knitting machine up to 85%
efficiency. However, by creating most suitable environment one can increase
machine efficiency.
For this we need following
figures:
Machine speed RPM
Machine guage
Machine Dia
Count/ denier of yarn being used
Stitch length
From the above-mentioned figures
we can calculate the length of yarn being used in one revolution and if we know
the length and count of yarn then it is quite easy to calculate weight of yarn
(see Example: 03 for more details)
Example 01
Calculate nominal production of a
single jersey-knitting machine per hour from the data given:
Machine Gauge 24
Machine Dia 30
inches
Number of Feeders 90
Machine RPM 26
Yarn Count 24
Stitch length 4
mm
Efficiency 85%
Solution:
Step
one
First we will calculate number of needles and number of stitches produced in one
revolution. This would help us in calculating the total length of yarn
consumed in one revolution.
Number of needles = machine dia *
gauge * p (3.14)
=
30* 24*3.14
=2260 (exact 2260.8
but needles are always in even number
so we will take nearest even figure)
Number
of stitches produced in revolution
Every needle is making one stitch on every feeder
because machine is producing single jersey fabric (full knit fabric).
Number of stitches produced in
one revolution = Number of needles * number of feeders
= 2260*90
= 203400
This figure shows that machine is
making 203400 stitches in one revolution.
Step Two
Length of stitch is 04 mm (stitch
length is always calculated in metric system)
From this figure we can calculate
yarn consumption in yards in one hour
Yarn Consumption (in yards) in
one hour
= number of stitches * length
of (mm) * RPM *60 (minutes)
1000(to convert mm into
meters)
=203400
* 4 * 26 * 60
1000
=
1269216 meters or
=
1388015 yards
Step Three
In previous step we calculated
quantity of yarn consumed in yards. We can easily calculate weight of this yarn
while its count is known (see example 03).
Weight of cotton yarn = length
of yarn
Count
* 840
=
1388015
840 * 24
=
68.85 pounds or
=
31.23 Kilo grams
Efficiency 85% = 26.55 Kilo
grams
Answer: this
machine can produce 26.55 Kgs fabric in one hour at 85 % efficiency
Example 02
For
Filament yarn, Calculate
nominal production of a single jersey-knitting machine per hour from the data
given:
Machine Gauge 28
Machine Dia 26
inches
Number of Feeders 120
Machine RPM 30
Yarn Denier 75
Stitch length 4.5
mm
Efficiency 85%
Solution:
Step
one
First we will calculate number of
needles and number of stitches produced in one revolution. This would help us
in calculating the total length of yarn consumed in one revolution.
Number of needles = machine dia *
gauge * p (3.14)
=
26* 28*3.14
=2286 (exact 2285.92
but needles are always in even
number so we will take nearest even figure)
Number
of stitches produced in revolution
Every needle is making one stitch on every
feeder because machine is producing single jersey fabric (full knit fabric).
Number of stitches produced in
one revolution = Number of needles * number of feeders
= 2286*120
= 274320
This figure shows that machine is
making 274320 stitches in one evolution.
Step Two
Length of stitch is 04.5 mm
(stitch length is always calculated in metric system)
From this figure we can calculate
yarn consumption in yards in one hour
Yarn Consumption (in yards) in
one hour
= number of stitches * length
of (mm) * RPM *60 (minutes)
1000(to convert mm into
meters)
=274320
* 4.5 * 30 * 60
1000
=
2221992 meters
Step Three
In previous step we calculated
quantity of yarn consumed in yards. We can easily calculate weight of this yarn
while its count/denier is known (see example 05).
Weight of filament in grams = Length in meters * denier 9000
=
2221992*75
9000
Answer
=18516
grams or
=18.516 Kgs
Efficiency 85% =
18.516*85%
=15.74 Kgs
Answer: this
machine can produce 15.74 Kgs fabric in one hour at 85 % efficiency
Note: if we are producing any
textured fabric, like fleece, then we use two different yarns at different
feeders and ultimately stitch length is also different. In such case we should
calculate separately consumption of different yarn at different feeders.
Following example will help in calculating production in case of use of more
than one kind yarn.
Example 9
Calculate nominal production of a
fleece-knitting machine per hour from the data given:
Machine Gauge 18
Machine Dia 30
inches
Number of Feeders for
60
Front yarn
Number of feeders 30
For loop yarn
Machine RPM 28
Yarn Count 26s for front
Yarn count for loop 16s
Stitch length of 4.5 mm
front yarn
Stitch length of 2.5 mm
Loop yarn
Efficiency 85%
Solution:
Step
one
First we will calculate number of
needles and number of stitches produced in one revolution. This would help us
in calculating the total length of yarn consumed in one revolution.
Number of needles = machine dia *
gauge * p (3.14)
=
30* 18*3.14
=1696 (exact 1695 but
needles are always in even number
so we will take nearest even figure)
In this example we will calculate
consumption of yarn in Kgs of both yarns and then we will add them to get final
production per hour
Consumption
of yarn for front knitting, Every
needle is making one stitch on every feeder because machine is producing single
jersey fabric (front of fleece).
Number of stitches produced in
one revolution = Number of needles * number of feeders =
1696*60
=
101760
This figure shows that machine is
making 101760 stitches in one revolution.
Step Two
Length of stitch is 04.5 mm
(stitch length is always calculated in metric system)
From this figure we can calculate
yarn consumption in yards in one hour
Yarn Consumption (in yards) in
one hour
= number of stitches * length of
(mm) * RPM *60 (minutes)
1000(to convert mm into meters)
=101760
* 4.5 * 28 * 60
1000
=
769305 meters or
=
841312 yards
Step Three
In previous step we calculated
quantity of yarn consumed in yards. We can easily calculate weight of this yarn
while its count is known (see example 03).
Weight of cotton yarn = length
of yarn
Count
* 840
= 841312
840 * 30
= 38.52 pounds or
= 17.43 Kilo grams
Efficiency 85% = 14.85 Kilo
grams
Answer: this
machine will consume 14.85 Kgs of yarn to knit front of the fleece fabric in
one hour at 85 % efficiency
Step Four
Yarn consumed
for loop knitting (back of the fabric)
Every needle is making one stitch
on every feeder because machine is producing single jersey fabric (front of
fleece).
Number of stitches produced in
one revolution = Number of needles * number of feeders
=
1696*30
=
50880
This figure shows that machine is
making 50880 stitches in one revolution.
Note: that we have put 30 cones
of course count for loops after every two feeders.
Step Five
Length of stitch is 2.5 mm
(stitch length is always calculated in metric system)
From this figure we can calculate
yarn consumption in yards in one hour
Yarn Consumption (in yards) in
one hour
= number of
stitches * length of (mm) * RPM *60 (minutes)
1000(to convert mm into meters)
1000
=
213696 meters or
=
233696 yards
Step Six
In previous step we calculated
quantity of yarn consumed in yards. We can easily calculate weight of this yarn
while its count is known (see example 03).
Weight of cotton yarn = length
of yarn
Count * 840
= 233696
840 * 16
= 17.39 pounds or
= 7.89 Kilo grams
Efficiency 85% =
6.70 Kilo grams
Step Seven
Now we can add both yarn consumed
Yarn for front 14.85
Yarn for back 6.70
Total 21.55
This machine
can produce 21.55 Kgs fabric in one hour at 85% efficiency
All above discussion to elaborate
the way to calculate the optimum production of a knitting machine. The
following formula is useful in every situation to calculate the optimum
production capacity of a knitting machine at 85% efficiency.
For cotton count
Production in one hour =
Gauge * Dia * 3.14 * RPM *60 *
Stitch length (mm) *1.0936 * 1 * 85
1000
*840 * yarn count * 100
Grammage Expressions
Generally grammage is expressed
in Grams per Meter Square (GSM) but in certain cases it is also expressed
Ounces per Yard Square (OSY). People, particularly working in marketing and
merchandising departments face problems in converting GSM into OSY. We will
explain this conversion method with examples before that it is imperative to
know the standard conversion factors of different measuring units. A complete
conversion chart is given at the end of the book. One should be much familiar
with these conversion factors.
Conversion
of GSM (grams per square meter) into OSY (ounces per square yard)
250 GSM means that weight of one meter square
fabric is 250 grams and 10 OSY means weight on one yard squares is 10
ounces. In the following lines we will
explain the method of conversion from GSM to OSY and vice versa with the help
of examples.
Example 10
Convert 10 OSY (ounces per square
yard) into GSM (grams per square meter).
It means weight of one yard
square is 10 ounces or
Weight of one square yard is 280
grams (one ounce is equal to 28 grams) or
Weight of one 0.836 meter square
(one yard square is 0.836 meter square) is 280 grams or
Weight of one meter square = 280* 1
0.836
Answer =
344.9 grams per meter square
Example 11
Convert 250 GSM (grams per square
meter) into OSY (ounces per square yard)
It means weight of one meter
square is 250grams or
Weight of one square meter is
8.93 ounces (28 grams are equal to one ounce) or
Weight of 1.196 yard square (one
meter square is equal to 1.196 yard square) is 8.93 or
Weight of one yard square = 8.93* 1
1.196
Answer =
7.47 ounces per yard square
Relation between length, width and grammage
It was observed during
interaction with the people working in garment business that they face
difficulties in calculation related to grammage, width and length of the
fabric. In the following lines we will explain relationship among these factors
with examples.
Example 10
Calculate weight of fabric from the given
data.
Grammage 300 GSM
Width of fabric 35 inches (in tubular form)
Length of fabric 20 meters
First we will calculate area of
the fabric
Area of fabric = Fabric length *
fabric width
= 20 * 35*2 (since fabric is in
tubular)
39.37 (one meter is equal to 39.37 inches)
=
35.6 meter square
Weight of one meter square is = 300 (GSM)
And weight of 35.6 meter square =
300*35.6
=
10680 grams or 10.680 Kgs
Example 13
Calculate GSM from the data given
Total Weight of fabric =
15.5 Kgs
Length of fabric
= 35 meters
Width of fabric in open form = 65 inches
Solution:
First we will calculate area of
the fabric
Fabric length = 35 meters
Fabric width = 65 inches or 1.65 meters
Fabric area = Length * width
=35
* 1.65
=57.75
meters square
Weight of 57.75 Meter square is 15.5 kgs or 15500 grams
So weight of one square meter = 15500/57075
= 268.39 grams per
meter square of GSM of
the fabric
Calculation of different fibre percentage in
knitted fabric
Normally fabrics are knitted with
one kind of yarn but in some cases more than one type of yarn of different
counts and combination (mixing of two different fibres) are used. One very
common example is knitting of fleece fabric, which is knitted by using fine and
course yarns, and one yarn is made of polyester and cotton. Another example is
knitting of fabric by using spandex filament and cotton or pure polyester. In such condition there is a requirement to
mention exact percentage of different fibres in the fabric. Supplier has to
mention this ratio on label. In the following lines we discuss the methods to
calculate such percentage with the help of examples.
Example
Find exact composition of
different fibres in fleece fabric from the following data:
Yarn count front 30s
100 cotton
Yarn count for loop 20s 50:50 P/C
Consumption ratio Front: loop 2:1 (by
weight)
Suppose for front we need 2Kg
yarn and for loop we will be requiring 1 Kg yarn
Front yarn 2
KGS 100 %
cotton Cotton 2000 grams
Loop yarn 1 Kg 50:50 P/C Cotton
500 grams and
Polyester
500 grams
Exact Ratio
Cotton total 2.5 Kgs
Polyester 0.5 Kgs
Ratio:
Cotton: 83.33%
Polyester : 16.66
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