Tuesday, August 9, 2011

Calculate nominal production of a fleece-knitting machine per hour

Learn Apparel Merchandising, Learn Fashion design.
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. We have develop a equation which is useful in evey 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 


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