KNITTING PRODUCTION CALCULATIONS

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 be 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) As per German DIN 62125, 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.

GAUGE vs YARN COUNT As a rule of thumb, knitting experts prefer to equate gauges near to count of yarn (English count) i.e. for 20- gauge machines most suitable yarn count is 20’s. This rule is has certain limitations, like, for 28-gauge, yarn of 26’s to 30’s 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 60’s double, which means that net count is near to 30’s, and is suitable for 30- gauge machine.

Some authors have suggested following formulas. For single Knitting Machine, Suitable count = E*E/18 For Double bed knitting machine, Suitable count= E*E/8.4 E = Gauge of machine Eg: Suitable yarn count for 12 gauge machine = 12 X 12 /18 (single bed) = 8’s

Knitting Machine Production Nominal Production of knitting machines One very simple way to calculate knitting machine production is by weighing the total production of one hour or one shift or one day. In this method, following information for production calculation are required:  Machine Gauge and Dia RPM Knitting Machine Yarn Count Stitch Length

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.

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 Tex Stitch length 4 mm Efficiency 85%

Solution: 1. 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 X gauge X  (3.14) = 30 X 24 X 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 one 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 X number of feeders = 2260 X 90 = 203400 This figure shows that machine is making 203400 stitches in one revolution.

2. Calculate yarn consumption in m in one hour. Length of stitch is 04 mm (stitch length is always calculated in metric system) Yarn Consumption in one hour = number of stitches X length of (mm) X RPM X 60 (minutes) 1000 (to convert mm into meters) = 203400 X 4 X 26 X 60 1000 = 1269216 meters

3. Calculate weight of this yarn while its count is known .   24 Tex = 1000 m of yarn weighs 24 gms therefore, 1269216 meters will weigh? Weight of cotton yarn (gm) = length of yarn (m) X tex 1000   = 1269216 X 24 1000 = 30461 gms Answer = 30.46 Kgs/hr

Production per hour is 30.461 Kgs Efficiency 85% = 30.461 X 85% =25.89 Kgs Answer: this machine can produce 25.89 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: 1. 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 X gauge X  (3.14) = 26 X 28 X 3.14 = 2286 (exact 2285.9 but needles are always in even number so we will take nearest even figure)

Number of stitches produced in one 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 X number of feeders = 2260 X 120 = 274320 This figure shows that machine is making 274320 stitches in one revolution.

2. Calculate yarn consumption in m in one hour. Length of stitch is 04 mm (stitch length is always calculated in metric system) Yarn Consumption in one hour = number of stitches X length of (mm) X RPM X 60 (minutes) 1000 (to convert mm into meters) = 274320 X 4.5 X 30 X 60 1000 = 2221992 meters

3. Calculate weight of this yarn while its count is known.   75 Den = 9000 m of yarn weighs 75 gms therefore, 2221992 meters will weigh? Weight of filament in grams = Length in meters X denier 9000 = 2221992 X 75 9000 Answer =18516 grams = 18.516 Kgs

Production per hour is 18.516 Kgs Efficiency 85% = 18.516 X 85% =15.74 Kgs Answer: this machine can produce 15.74 Kgs fabric in one hour at 85 % efficiency.

Note: If we are producing a double bed fabric, then we shall calculate the total number of needle in cylinder and dial. The total number of stitches should be based on this. If we use two different yarns at different feeders, the ultimately stitch length is also different. In such case we should calculate separately the consumption of different yarn at different feeders.

Example 03 Calculate nominal production of a 1X1 rib machine per shift (8 hrs) from the data given: Machine Cylinder Gauge 24 Machine Dia 30 inches Number of Feeders 50 Machine RPM 25 Yarn Count 25 Tex Stitch length 3 mm Efficiency 82%

Solution: 1. 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 X gauge X  (3.14) = 30 X 24 X 2 X 3.14 = 4522 (exact 4521.6 but needles are always in even number so we will take nearest even figure)

Number of stitches produced in one 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 X number of feeders = 4522 X 50 = 226100 This figure shows that machine is making 226100 stitches in one revolution.

2. Calculate yarn consumption in m in one hour. Length of stitch is 03 mm (stitch length is always calculated in metric system) Yarn Consumption in one hour = number of stitches X length of (mm) X RPM X 60 (minutes) 1000 (to convert mm into meters) = 226100 X 3 X 25 X 60 1000 = 1017450 meters

3. Calculate weight of this yarn while its count is known.   25 Tex = 1000 m of yarn weighs 25 gms therefore, 1017450 meters will weigh? Weight of cotton yarn (gm) = length of yarn (m) X tex 1000   = 1017450 X 25 1000 = 25436.25 gms Answer = 25.436 Kgs

Production per hour is 25.436 Kgs Production per shift = kgs/hr X hrs/shift = 25.436 X 8 = 203.49 kgs Efficiency 82% = 203.49 X 82% =166.86 Kgs Answer: this machine can produce 166.86 Kgs of 1X1 rib fabric in one shift of 8 hours at 82 % efficiency.

What about the production of a 3 X1 rib. How do you calculate the number of stitches?

Exercise 01 Calculate nominal production of a 3X1 rib machine per shift (8 hrs) from the data given: Machine Cylinder Gauge 24 Machine Dia 30 inches Number of Feeders 50 Machine RPM 25 Yarn Count 25 Tex Stitch length 3 mm Efficiency 82%

What about the production of a half Milano. How do you calculate the number of stitches?

What about cases where: Tuck and knit structures in one course Different yarn used for different feeders? Eg stripe effect Intarsia knit

Assignment Calculate nominal production of a half Milano machine per shift (8 hrs) from the data given: Machine Cylinder Gauge 24 Machine Dia 30 inches Number of Feeders 60 Machine RPM 20 Yarn Count 24 Tex Stitch length 4 mm Efficiency 85%