10 Weft Knitting Production Calculations PDF

Basics of knitting - Production calculations I n any manufacturing process, the calculations regarding production, efficiency and material requirements are primary importance. In knitting industry also calculations mainly deals...

Basics of knitting - Production calculations I n any manufacturing process, the calculations regarding production, efficiency and material requirements are primary importance. In knitting industry also calculations mainly deals As speed factor (rpm x diameter in inches) The circumferential speed in meters per second is a constant for a range of machine diameters of the same model and can be with productions, machinery requirements, raw material used to calculate the rpm for a particular machine diameter requirements and the costing of the finished products, so as to An average circumferential speed is about 1.5 m/sec; 2 m/sec determine the competitive selling price, will mainly depend upon is ‘high speed’ the correct calculations. Modern high-speed fabric machines can operate in factory Below are the most important circular knitting machines conditions at speeds of 1.6 to 1.7 m/sec. calculations: Under laboratory conditions, speeds of 2.0m/sec have been achieved Machine speed Number of feeds Number of feeds Speed of fabric production The number of feeds can be expressed as a total for a particular Weight of fabric produced cylinder diameter or as the number of feeds per inch of the cylinder diameter, in which case the total number of feeds for Machine speed any cylinder diameter in that particular range of machinery can The speed of a circular machine may be expressed in three ways: then be calculated. As machine revolutions per minute Production calculations The machine revolutions per minute are only relevant to a Among the various factors those are to be considered in the specific machine and machine diameter. A larger-diameter manufacture of knitted fabrics, it is very important for the knitter machine or one having more patterning facilities, would be to calculate the productivity of a machine in order to be able to expected to run at less revolution per minute schedule production and specify the delivery dates to the As circumferential speed in meters per second customer. Selected examples are given in this chapter to The circumferential speed in meters per second is a constant understand the methods of calculating production and efficiency for a range of machine diameters of the same model and can be of machines used for weft knitting productively in weft knitting used to calculate the rpm for a particular machine diameter terms refers to the length of the fabric that comes out of the An average circumferential speed is about 1.5 m/sec; 2 m/sec machine the width of the fabric both single and double width is ‘high speed.’ and the weight of the fabrics produced in unit time.  Production of knitted fabric may be calculated either in length, Machine parameters i.e. yards or meters, or in weight, e.g. kg, per unit time. One of i. Machine speed (rpm) the most popular methods is calculating the weight of the fabric ii. Machine diameter (inches) produced in one hour or one shift. From these figures, the iii. Machine gauge (Needles/inch) length of yarn can be calculated which is being used by the iv. Number of feeders machine in one hour and then by converting this length into v. Machine efficiency weight with the help of count given, the quantity of yarn being vi. Number of needles consumed by machine in one hour can be calculated. This would be the optimum production of the machine. This optimum Yarn and fabric parameters production can be converted into nominal production by i. Yarn count multiplying it with efficiency. ii. Stitch length/loop length iii. Stitch density The following are the important parameters, which decide the iv. Wales per inch production calculations of circular weft knitting. v. Courses per inch There are various methods available to calculate production of circular knitting machine Formulas Weight of fabric produced Method 1 No. of working feeders x RPM x GSM x Fabric open width in mtr x 13.50 Production in Kg per day @ 100 per cent efficiency = Feeders per course x Stitches per cm x 1000 Method 2 No of working feeders x RPM x 60 Production in yards per hour @ 100 per cent efficiency = Course per inch x 36 Method 3 Number of needles per inch x Stitch length in inches x Courses per inch x 1000 Fabric weight per liner yard = Count Ne x 840 x 2.2 Method 4 Weight per linear yard x 36 Fabric weight per square yard = Fabric width in inches Grams per square meter (GSM) Method 1 GSM = Stitch density (cmloop sqx Loop length (mm) x Count (Tex)100 Method 2 Ks x count (Tex) GSM = Stitch length (mm) Where, Ks is a constant. Its value is different for different fabric structure and fabric type. Ks is calculated and estimated as below:  GSM x Stitch length (mm) Yarn diameter Ks = Count (Tex) Fabric type Values of Ks 0.375 Single jersey 19.55 d  x Tex For Direct System  1 x 1 rib 24.5 100 Polo pique 25 or Plain interlock 39.3 d N For Direct System 1 𝑑= 𝑖𝑛𝑐ℎ. [𝐹𝑜𝑟𝐼𝑛𝑑𝑖𝑟𝑒𝑐𝑡𝑆𝑦𝑠𝑡𝑒𝑚] (28√𝑁𝑒) 𝑜𝑟 1 𝑑∞ √𝑁 Length of fabric produced RPM x no.of feeder x 60 Fabric thickness Fabric length in yard/hour = Fabric thickness (SJ) = 2 x yarn diameter Courses per inch x 36 Fabric thickness (DJ) = 4 x yarn diameter Loop length Count (Tex) Fabric diameter (Tubular) Loop length = K Machine diameter x Machine gauge Fabric diameter (Tubular) = Where K = Constant factor 7 x Count (Ne) Course length Yarn length per stitch Course length = Loop length x Number of needle per course Yarn length per course Yarn length/stitch = Fabric width Number of needles Number of stitches in course Fabric width (cm) = Yarn length per course Wales per cm Yarn speed (inches/min) Stitch density Yarn length/course = Machine speed (RPM) Stitch density = Courses per cm x Wales per cm Feeder density Number of feeders Feeder density = Machine diameter Fabric width No. of needles Feeder density = Wales per inch