Knitting calculations - Most suitable count for knitting machines

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 calcul

KNITTING CALCULATIONS

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 onecan increase machine efficiency

For this we need following figures:

consumed in one revolution.

Number of needles = machine dia * gauge * π (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

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

Answer: this machine can produce 26.55 Kgs fabric in one hour at 85 % efficiency

consumed in one revolution.

Number of needles = machine dia * gauge * π (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

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

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

Number of needles = machine dia * gauge * π (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

= 101760This 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

= 50880This 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)

=50880 * 2.5 * 28 * 60 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

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

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 ofexamples

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

0.836Answer = 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 8.93or

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 thatthey 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

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) areused 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