How to get the required width and weight of knitted fabric

A Reader has posed this query to me:

"We have difficulties in getting the required width and weight of the knitted fabric we make. In our knitting machine we are using guage 24, 100% cotton yarn, Ne 30/1.
1) What is the weight of the unfinished fabric we should make ?

2) shall we keep the unfinished knitted fabric (100% cotton) for a certain period of time prior the dyeing or bleaching process ? If yes, then how many hours ?

3) In the calendering process: shall we change the width of the fabric which we recieve from the dyeing process ?? For example, if the width of the knitted fabric after dyeing/bleaching is 88 cm. Shall we keep the same width during the calenderig process or shall we increase it ??

4) Shall we keep the unfinished knitted fabric for a certain period of time prior we transfer it to production (cutting & sewing) ??? if yes, how many hours ??

5) When is the best time for measuring knitted fabric weight ?? Is it immediately after the knitting process and after the bleaching process ?? or shall we wait for some hours or days till the fabric take it's final shape after both processes ??? "


I welcome your comments.

How to Control Skew on Single Jersey Circular Weft Knitted Fabrics

Ideally courses and wales should be at right angle to each other. Skew occurs when wales are displaced from their vertical position when it is called wale skew. It also occurs when courses are displaced from their horizontal position when it is called course skew.

Skew on 100% cotton single jersey is related to the level of yarn twist, the spinning system used, the strand configuration, the tightness of the knitted stitch, the number of feeders on the knitting machine, the rotational direction of the knitting cylinder and the finishing techniques used.

Normally skew caused by yarn is wale skew and that caused by feeders is course skew.

Skew is measured using a proposed test method developed by AATCC. In this test the samples are marked with a square before washing and tumble drying. If the fabric skews after five wash and dry cycles, the square can be measured for percent skew.

 The method uses a mathematical formula for shear distortion (skew) and is shown below: % skew = 2(AC-BD) x 100/(AC + BD) Where AC and BD are the diagonals of the square.

On a knitting machine making single jersey. For each feed of yarn, one revolution of the machine will make a course of fabric. The more the number of feeders, the more courses are made in one revolution of machine. Which means that the courses are stacked on top of each other for each revolution. This creates a spiral line as shown in the figure. The distance between the spiral lines represent the production of courses for one revolution of cylinder. Thus for example if in one revolution of cylinder there is a formation of 1.5 inches of linear meter of cloth then there will be 1.5 linear inches of skew in the course that is generated. Machines with large numbers of feeders can create substantial skew in the fabric.

It is important to note that skew from the yarn and the skew from the number of feeders in the machine can combine together to create more skew or can offset the skew. Thus while selection of yarn twist according to the direction of rotation of cylinder is very important. In general, yarns with Z twist gives less skew on a machine of counterclockwise rotation. It is due to the fact that fabric coming from the counterclockwise machine have courses with LH skew while yarns with “Z” twist yield fabrics with RH skew. This offsets the two skews and the resulting fabric is more balanced.

It is said that best skew qualities result by alternating feeds of S and Z twist. Taking plied yarn instead of single yarn can also control the skew. If single yarns must be used, then resin finishing offers reasonable control of skew.

Also it is found that higher the twist multiple, the greater is the tendency to skew. All Z twist cotton yarns exhibit skew in a direction referred to “right-hand skew”. It means there is a wale loop distortion that leans to the right. All S twist yarns yield a left hand skew.

In general open-end yarns result in less skew than the ring spun yarns.

Also the tighter the stitch means more the number of stitches per revolution, the less is the skew.

Source: Technical Bulletin- Knit Fabrics and the Reduction of Torque

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How to Control GSM in a Single Jersey Knit Fabric

This is a question asked by one of my readers. To answer this, we start from the first principles.

Knitting is a process of fabric forming by the intermeshing of loops of yarn. When one loop is drawn through another, loopstitch is formed.

Weft knitting is a method of forming a fabric in which the loops are made in horizontal way from a single yarn and intermeshing of loops take place in a circular or flat form or acrosswise basis.

Single Jersey is a weft knitted fabric produced with one set of needles is called single Jersey or plain knitted fabric.

GSM can be controlled either by taking a coarse count of yarn. Or for the same count of yarn increasing the stitches per inch. Stitch per inches can be increased by either resorting to a higher gauge machine or by decreasing the loop length.

In modern weft knitting machine there is a positive feeder called IRO which regulates the speed of the fed yarn. If the speed of IRO increases, the quantity of yarn passing in the m/c increases, so the loop size increases and hence the GSM decreases. If the speed decreases the reverse happens and the GSM increases.

The loop size can also be decreased by adjusting the distance between the cylinder and the dial needles: If the distance is more the loop size increases and hence the GSM decreases.

To get a first lesson on knitting please revert to this chapter. 

As a bonus let us watch this song in which close to 720 intarsia knit fabrics are used:

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Spirality and Skew in Single Jersey- Causes and Remedies

This question is posted in a discussion by one of the readers:

I need a solution to control the skew and spirality of single jersey 160g with 30/s. Please provide me with some solution 

Spirality is a dimensional distortion in circular knitted fabric. Spirality is bad as it leads to displacement of seams and mismatched patterns. It can also leads to sewing difficulties. The major cause of spirality is the twist in roving and yarn. To minimize spirality, Z-twist yarns should be knotted on clockwise rotating machine and S-twist yarns on counter clockwise rotating machines. Tighter Fabics exhibit less spirality compared to looser fabrics which means that finer gauge machines will reduce spirality.

It can also be reduced by setting the twist either by autoclave treatment, yarn dyeing or using balanced plied yarns. 

For more information SITRA has a nice Technical brief here

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Common Knit Fabrics

What are commonly Used Knit Fabrics: An answer to this can be found in the following table and the description given below it:

KNITTED FABRIC DESCRIPTIONS
CONTENT	YARN COUNT	FABRIC TYPE	GSM RANGE
100% Cotton	40s Combed	Single-Jersey	100-120
100% Cotton	36s Combed	Single-Jersey	110-130
100% Cotton	30s Combed	Single-Jersey	140-155
100% Cotton	26s Combed	Single-Jersey	160-170
100% Cotton	24s Combed	Single-Jersey	165-180
100% Cotton	20s Combed	Single-Jersey	180-200
100% Cotton	18s Combed	Single-Jersey	210-230
100% Cotton	16s Combed	Single-Jersey	230-250
100% Cotton	40s Combed	Slub-Jersey	100-120
100% Cotton	36s Combed	Slub-Jersey	110-130
100% Cotton	30s Combed	Slub-Jersey	140-155
100% Cotton	26s Combed	Slub-Jersey	160-170
100% Cotton	24s Combed	Slub-Jersey	165-180
100% Cotton	20s Combed	Slub-Jersey	180-200
100% Cotton	18s Combed	Slub-Jersey	210-230
100% Cotton	16s Combed	Slub-Jersey	230-250
95/5 Cotton/Spandex	40s Combed + 20-Danier	Single-Jersey	160-180
95/5 Cotton/Spandex	32s Combed + 20-Danier	Single-Jersey	190-200
95/5 Cotton/Spandex	30s Combed + 20-Danier	Single-Jersey	200-210
95/5 Cotton/Spandex	30s Combed + 30-Danier	Single-Jersey	220-230
100% Cotton	30s Combed	Pique	180-190
100% Cotton	26s Combed	Pique	190-200
100% Cotton	24s Combed	Pique	200-220
100% Cotton	20s Combed	Pique	210-240
100% Cotton	18s Combed	Pique	240-250
100% Cotton	16s Combed	Pique	260-280
95/5 Cotton/Spandex	40s Combed + 40-Danier	Pique	180-200
95/5 Cotton/Spandex	30s Combed + 40-Danier	Pique	240-250
100% Cotton	40s Combed	1X1 Rib	140-160
100% Cotton	30s Combed	1X1 Rib	180-200
100% Cotton	26s Combed	1X1 Rib	210-220
100% Cotton	24s Combed	1X1 Rib	220-240
100% Cotton	20s Combed	1X1 Rib	250-270
100% Cotton	16s Combed	1X1 Rib	300-340
97/3 Cotton/Spandex	30s Combed + 30-Danier	1X1 Rib	220-240
97/3 Cotton/Spandex	30s Combed + 40-Danier	1X1 Rib	230-250
97/3 Cotton/Spandex	26s Combed + 40-Danier	1X1 Rib	260-280
97/3 Cotton/Spandex	20s Combed + 40-Danier	1X1 Rib	300-330
100% Cotton	40s Combed	2X2 Rib	140-160
100% Cotton	30s Combed	2X2 Rib	180-200
100% Cotton	26s Combed	2X2 Rib	210-220
100% Cotton	24s Combed	2X2 Rib	220-240
100% Cotton	20s Combed	2X2 Rib	250-270
100% Cotton	16s Combed	2X2 Rib	300-340
97/3 Cotton/Spandex	30s Combed + 30-Danier	2X2 Rib	220-240
97/3 Cotton/Spandex	30s Combed + 40-Danier	2X2 Rib	230-250
97/3 Cotton/Spandex	26s Combed + 40-Danier	2X2 Rib	260-280
97/3 Cotton/Spandex	20s Combed + 40-Danier	2X2 Rib	300-330
97/3 Cotton/Spandex	40s Combed + 40-Danier	2X2 Rib	180-200
97/3 Cotton/Spandex	30s Combed + 40-Danier	2X2 Rib	210-220
97/3 Cotton/Spandex	26s Combed + 40-Danier	2X2 Rib	220-240
97/3 Cotton/Spandex	20s Combed + 40-Danier	2X2 Rib	250-270
100% Cotton	40s Combed	Interlock	180-200
100% Cotton	30s Combed	Interlock	220-240
100% Cotton	26s Combed	Interlock	240-260
100% Cotton	24s Combed	Interlock	270-280
100% Cotton	20s Combed	Interlock	300-320
100% Cotton	16s Combed	Interlock	330-350
100% Cotton	40s Combed	Brushed Back Terry	160-170
100% Cotton	30s Combed	Brushed Back Terry	180-200
100% Cotton	26s Combed	Brushed Back Terry	200-210
100% Cotton	24s Combed	Brushed Back Terry	220-230
100% Cotton	20s Combed	Brushed Back Terry	240-260
100% Cotton	16s Combed	Brushed Back Terry	280-290
95/5 Cotton/Spandex	40s Combed	Brushed Back Terry	180-200
95/5 Cotton/Spandex	30s Combed	Brushed Back Terry	210-220
95/5 Cotton/Spandex	26s Combed	Brushed Back Terry	220-240
95/5 Cotton/Spandex	24s Combed	Brushed Back Terry	250-270
95/5 Cotton/Spandex	20s Combed	Brushed Back Terry	280-300
95/5 Cotton/Spandex	16s Combed	Brushed Back Terry	310-330
100% Cotton	40s Combed	Loop Back Terry	160-170
100% Cotton	30s Combed	Loop Back Terry	180-200
100% Cotton	26s Combed	Loop Back Terry	200-210
100% Cotton	24s Combed	Loop Back Terry	220-230
100% Cotton	20s Combed	Loop Back Terry	240-260
100% Cotton	16s Combed	Loop Back Terry	280-290
95/5 Cotton/Spandex	40s Combed	Loop Back Terry	180-200
95/5 Cotton/Spandex	30s Combed	Loop Back Terry	230-250
95/5 Cotton/Spandex	26s Combed	Loop Back Terry	260-270
95/5 Cotton/Spandex	24s Combed	Loop Back Terry	280-300
95/5 Cotton/Spandex	20s Combed	Loop Back Terry	300
95/5 Cotton/Spandex	40s+40s Combed + 20-Danier	French-Terry	180-200
95/5 Cotton/Spandex	30s+30s Combed + 20-Danier	French-Terry	240-260
80/20 Cotton/Poly	30s+30s Combed + 10s PC	3-Fleece	300-340
80/20 Cotton/Poly	30s+30s Combed + 10s PC	3-Fleece	280-300
80/20 Cotton/Poly	20s Combed + 10s PC	2-Fleece	260-300
100% Cotton	40s Combed	Waffle	140-160
100% Cotton	30s Combed	Waffle	180-200
100% Cotton	26s Combed	Waffle	210-220
100% Cotton	24s Combed	Waffle	220-240
100% Cotton	20s Combed	Waffle	250-270
100% Cotton	16s Combed	Waffle	300-340
100% Cotton	40s Combed	Thermal	140-160
100% Cotton	30s Combed	Thermal	180-200
100% Cotton	26s Combed	Thermal	210-220
100% Cotton	24s Combed	Thermal	220-240
100% Cotton	20s Combed	Thermal	250-270
100% Cotton	16s Combed	Thermal	300-340

How to Identify a Jersey, Rib and Interlock Fabric

A very easy to understand identify the three is given here.

See an example of Brushed Back Terry here
See an example of French Terry here
See an example of Waffle Knit here
See an example of Thermal Knit Here

What is 3-Fleece and 2-Fleece

Three end and two end, course cut (10 to 14), knitting techniques are conventionally used to produce knitted fleece with low stitch densities (600-700). Fabric with a higher stitch density is generally perceived to be a higher quality fabric because it has a lower shrinkage rate and a more stable print platform.

The term "stitch density" is frequently used in knitting instead of a linear measurement of courses and wales, it is the total number of needle loops in a square area measurement such as square inch. It is obtained by multiplying the number of courses per inch by the number of wales per inch. Stitch density tends to be a more accurate measurement because tension acting in one direction in the fabric may, for example, produce a low reading for the courses and a high reading for the wales, which when multiplied together cancel the effect out.

Two end, course cut knitting techniques are generally used to produce knitted fleece fabric with lower stitch density, which is generally perceived to be low quality fabric. Two end knitted fleece fabric constructions are typically less costly to produce compared to three end knitted fleece fabric constructions because of lower yarn material costs.

Both three end and two end course cut knitting techniques can be used to produce knitted fleece fabric having the same fabric weight and the same stitch density. However, because three end knitting uses three yarn ends, as opposed to two yarn ends used by two end knitting, a yarn having a finer yarn count, which is significantly more expensive, is necessary to produce knitted fleece fabric with the same fabric weight and same stitch density. Thus, it is much more costly to produce knitted fleece fabric of a given weight and stitch density using a three end knitting technique. See a patent based on this information here.

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