Machines used for knit fabric production

In apparel industry, knitting machine used for producing knitted fabric like single jersey, pique, fleece, terry and so on. There are two types of knitting machine used to produce knit fabric, flatbed knit machine and circular machine. Actually, knitting machine is a device, that used to make fashionable product.  Presently, circular machine uses more than flatbed machine uses. Flatbed machine helps to make parts like collar, cuff & pockets etc. for garments. As we already discuss on bellow topic;

• Basic structure of knit fabrics
• Commonly used knit fabrics for garments

Now we will discuss about flatbed machine and circular machine. There are two types of knitting machines are used to produce knit fabric:

1. Flatbed knitting machine
2. Circular/tubular type knitting machine

A.      Flatbed knitting machine:

In garments sector, to produce knitting flat pieces, flatbed machine is one of the common knitting machine. A flat-formed fabric with straight edges or sides produced on a flat-bed machine. Also note that, flatbed machine can’t purl stitch automatically. Because flatbed knitting machine have horizontal needle beds. We call it flat knit as opposed to circular knit. We usually use flat knit for collar cuff and bottom of knit shirts or sometimes jackets too. When we use flat knit collar, cuff and bottom, we usually would knit them to the exact sizes because as we know, they should not be cut for size adjustment.

B.      Circular/tubular knitting machine:

Now-a-day, circular/tubular machine is used widely for producing knitted fabric in the knitting mills. All over the world, majority of knit fabrics are produced on circular knitting machines. A tubular or circular fabric produced on a circular-type knitting machine with the loop stitch formation process made around the fabric. Needles on the knitting machine are arranged in circle, producing fabric in tubular form. Goods may be produced as tubular yard good or circular-shaped components or trimmings. Most knitted fabrics, are of circular knit which means before it is cut open, the circumference is about 60”. After knitting is completed and finished, you cut it open and width becomes about 60”.

When you set the width /Dia. by machine, you may stretch it to 62” or 64”. There is a flexibility of about 6” you can play with to suit the garment chest measurement of your size specifications. Therefore, before you specify the width of the knitted fabric for the knitting mill to follow, you should study your garment size specifications to determine what width you need to minimize the cutting loss.

Not only you can stretch the width, you can also stretch the length and set it, so that the width is wider and the length is longer. Since you buy knitted fabrics by weight (by pound or kg), now that you have stretched the fabric width wise and lengthwise, you seem to have benefited from this manipulation. Unfortunately, the truth of the matter is, you are taking a very dangerous step because what you do may bring you big problem later.

1. When you stretch the width and length, the weight of the fabric per square meter will be reduced, you may be making the fabric too light beyond the buyer’s acceptance.
2. When you stretch the width and length excessively, you are making the holes in the fabric bigger than normal, the fabric may have a see through effect.
3. No matter the fabric is of 100% cotton, or cotton / polyester blend, when you stretch it excessively, it will recover to an extent

When it is relaxed or washed, garments made of this over stretched fabric may not pass the buyers test, nor even be found acceptable at the consumer level due to excess shrinkage. We should not try to gain the extra profit by stretching the fabric excessively. If we need wider width on the fabric to achieve better yield we should try to set the machine to knit wider width, and not to make up the normal width and then stretch it and set it. It is dangerous to do so.

Starching the selvedges of knit fabrics:

When you order knitted fabrics of medium to light weight, you should consider to instruct the mill to starch the selvedge (to make both edges of the fabric inflexible so that they will not curve up) without starching the selvedges, you may find the two sides of the fabric, curved up on the cutting table, making it very difficult to lay the fabric neatly for cutting. 

Commonly used knit fabrics for garments

Actually knitting fabric can be made by hand or by using a machine. Presently, knitting machine used more than hand knitting. There are variety of knitted fabrics available in the market. In apparel industry, knitted fabrics are used for producing knitted garments like T-Shirt, Polo shirt, Sweater, Sweatshirt, children’s wear etc. For producing different type of knit fabrics, mills used different type of construction & specification. We already discussed about basic structure of knit fabrics.

Now we will discuss the following list of names of knit fabrics which are commonly used to produce knit garments:

1. Plain/ single/ jersey knit
2. Pique knit / Lacoste knit
3. Interlock knit
4. Rib knit
5. Terry knit
6. Fleece knit
7. Jacquard knit
8. Yarn dyed stripe knit
9. Feeder stripe knit
10. Engineered stripe knit

Plain / Single / Jersey knit:

People call it jersey knit. A weft knit process producing a plain, flat-surfaced knitted fabric designed with a separate face and back. A single-faced knitted fabric designed by an interlinking of stitches in the same direction on the face and a series of semicircular loops produced on the reverse or back. Even-patterned loops are produced in the lengthwise direction on the face of the fabric and even patterned, wavy loops in the crosswise direction on the reverse. Jersey knit process utilizes both single and double yarn construction.

Pique Knit:

Pique Knit fabric manufacturing by weft technique. Basically, Pique fabrics used for Men’s polo shirt & women’s polo shirt. It’s also used for manufacturing sportswear.  

Interlock stitch knit:

A weft knit process producing a compound fabric. Two separate 1x1 rib fabrics are interlocked or inter knitted to form one cloth. The two rib course are defined as one interlock course, since together they produce one stitch in every wale. Interlock stitch knit process utilizes single yarns in the knitting process. Same appearance on face and back and double faced. When needle heads are facing with each other, then it is called interlock gating, that means interlock fabric.

RIB knit:

A weft knit process producing a double faced fabric. Rib knit is made with two sets of needles producing alternate plain and purl stitches that join in opposite directions in the lengthwise direction and produce separate vertical ribs on both sides of the fabric. Rib knit process produces high and low areas with stitches alternating up and over and down and under creating a corrugated effect. There are 1 by 1 rib, 2 by 2 ribs, 3 by 1 rib, 5 by 2 ribs and so on. You count the number of ribs in front and on back to determine what it is.

Terry knit:

A woven or knit uncut loop structure produced as single faced with loop formation on face and back. Size, shape and density of loop formation may vary. It looks like terry towel.

Fleece knit:

One side looks like jersey, the other side heavily brushed. Also note that, the inside of fleece fabrics brush can be light or heavy, buyer will confirm their requirement of brush. Fleece fabric’s contraction can be 100% cotton, 80% cotton 20% poly etc (As per buyer requirement). Actually buyer will confirm which contraction used to make the fabric. Also note that, normally fleece fabric GSM is higher, than the normal other knitting fabrics. Please note when knitted fabrics are finished by the mill, it is usually rolled on a tube with tension.

Therefore, when you unroll the fabric on the cutting table, you should not apply the marker on and cut it right away, you should let it relax for a few hours, or preferably over night to check if the length has become shorter when the tension is gone. If may surprise you that the length or the width or both have shrunk 5 to 7% on the cutting table. Just imagine, if you cut the fabrics without relaxing then you many end up getting your garments undersized. The degree of such shrinkage is contingent on the tension it was given prior.

Jacquard knit:

Jacquard knit is a system of producing a patterned knit fabric combining the jacquard system. The system is the individual control of the selection of the needles to produce the design or pattern utilizing.

• Punch cards or programmed techniques similar to woven Jacquard fabric
• Electronic or electromagnetic devices
• Can be produced by warp or weft type method of knitting fabric
• Produces single or multicolored designs and patterns
• Designed with a flat or raised surface
• Can be hard finished or smooth texture or brushed for napped finish
• Produces jacquard blister knit, jacquard jersey knit and jersey knit variations, jacquard rib knit and rib knit variations.

Yarn dyed stripe knit:

Generally, we collect the yarn from yarn supplier or spinning mills then we produce the fabric from grey yarn that is called grey fabric. After that, we dye the fabric in any color as per buyer requirement. But after collecting the yarn from yarn supplier or spinning mills & send the yarn for dying purpose as per buyer requirement color. On the other hand, we can collect direct dyed yarn from spinning mill. That means we dyed the yarn before produce the knit fabric, that is called yarn dyed fabrics.

In making color knitted fabrics, we usually would use the following methods to color them:

• Piece dye: for solid colors
• Yarn dye: for horizontal stripes
• Printing: for printed designs

For piece dyed solid colors and prints, the process of manufacture is pretty much the same as woven fabrics. However, on yarn dyed stripes it is important we know the following:

Feeder stripe knit:

This means you feed the knitting machine with yarn of different colors and let the machine knit as knitting solid color fabrics. The knitting machine has a capability for 108 cones of yarn. Now you have inserted 8 cones of black yarn in to it, with the balance 100 cones white yarn. After getting start knitting you will find out that, there is a black horizontal stripe within 2”.

From the above example you can understand that within the 108 spaces, you have inserted 8 cones of black color yarn to form a horizontal stripe design that you have worked out. You can also see that the size of repeat is about 2”. If this is a fine yarn used, it could be smaller than 2”, if it is a thick yarn used, it can be bigger than 2”. There is no limit about the number of colors you can use within the 2” repeat. For example, you can use 108 different colors if you wish. There are knitting machines of more than 108 cones and machines of less than 108 cones. So, the 2” repeat is a little flexible.

Engineered stripe knit:

When the size of the repeat of the stripe you need is bigger that 2” it is beyond the feeder stripe method can do and you will have to use “Engineered stripe” method to make this knitted fabric. In this engineered stripe method, the machine is set to change threads at certain time to from a big repeat. This way the repeat can be of almost any size. However, the price of engineered striped fabric is substantially higher than the normal stripe price. Therefore, as garment merchandisers, when we get the artwork from buyer & artwork showing, for example, a 2-3/4” repeat, we should check with the knitting mill to find out how close we can get the repeat to 2-3/4”, or check with the buyer if they could let you shrink it down from 2- ¾“ to 2 ½“ before you choice to engineered stripe method. However, if the repeat given in the artwork is 14” and buyer don’t want to change it in any way, for example, then you should use engineered stripe method without any choice. 

Basic structure of knit fabrics

Knitted fabrics are an alternative to the woven or loom fabrics. These fabrics are stretchable, soft and quick to recover from wrinkles, unlike, woven fabrics knitted fabrics would not become stiff or board even if you make it heavy. All knitted fabrics (except warp knit) are stretchable in both directions horizontal and vertical, but more stretchable horizontally. Knit fabric structures are formed through the process of interlocking loops or forming loops with one or more yarn in preceding and succeeding rows, knit fabrics are produced by hand or on a variety of knitting machines with one or more needles of different types.

Variation of knit fabrics may be achieved by adding deleting or combining any one or more of the following:

• Content of fiber – natural, man-made, blend or combination
• Type of fiber – filament or staple
• Size or denier of yarn – fine, lofted or bulked
• Type of yarn – twisted, textured, novelty or specialty
• Color of yarn – one color or multi colored
• Type and capability of knitting machines
• Attachments used on knitting machines
• Type and quality of needles
• Size, thickness and length of needles
• Formation of needles – inoperative or selectively operative
• Number and spacing of needle sets
• Size of stitches
• Formation and pattern of stitches
• Number or threading of guide bars
• Finishing processes applied to yarn or finished goods

Any variation of the above will affect the appearance, texture, performance expectation and weight of the fabric.

Knit fabrics are classified and named with regard to the

• Structure of fabrics
• Method or type of production or construction
• Type of machine used for its construction
• Number of guide bars on a machine

According to the basic structure of knit fabrics, knit fabrics are classified into two categories:

1. Warp knit fabric and
2. Weft knit fabric

1. Warp knit fabrics:

This is a special kind of knit fabric which has warp treads (but no weft threads).  This fabric has little or no stretch ability like woven fabric. It is called knit, because it is constructed by needles like other knits fabric and it has no weft threads. It feels like woven fabric and wears like woven fabric, warp knit fabrics are produced by a system of interlocking loops in a length wise direction. Fabric is produced by several parallel yarns that form one stitch for each yarn in each course. Each stitch in a course is made by different yarn. All the needles move up to at the same time to make the stitch. The stitches are produced in each course simultaneously. Warp knit structures as following kinds:

• Milanese knit
• Raschel knit
• Ketten raschel knit
• Tricot knit

Milanese knit: Milanese knit fabric is more expensive than tricot fabric. It’s also stronger, stable and smoother than tricot fabric. Milanese fabric stitches very similar to tricot fabric. It can be identified by face fabric having a fine vertical rib and the opposite having a diagonal structure.

Raschel knit: Raschel knit do not stretch significantly and used for coats, jackets and dresses. Raschel knitting is done by heavy yarns and usually has a complex lacelike pattern.  

Kitten rashel knit: Kitten rashel knit is fine with good elasticity. Kitten rashel knit also known as chain rashel.

Tricot Knit: Tricot knit fabric is very soft. It is used for verity of fabric weights and design. There are many types of tricot fabric- plain tricot, satin tricot, mesh tricot etc. Tricot fabric used in shirts, blouses and dresses. 

2. Weft knit fabrics:

These fabrics are produced by a system of interlocking loops in a cross wise direction. The loops are made in horizontal courses with each course built on top of the other. All the needles operate independently of one another and all the stitches in the course are made by one yarn. These fabrics are usually constructed horizontally by needles without warp yarn. As merchandisers to handle knit garments we should first learn to be able to identity the different kinds of knit and what the limits are of what you can do of each kind. When knit fabrics are finished by the mill, it is usually rolled on a tube with tension. Therefore, when you unroll the fabric on cutting table, you should not apply the marker on and cut it right away, you should let it relax for a few hours, or preferably over night to check it the length has become shorter when the tension is gone. It may surprise you that the length or width or both have shrunk 5 to 7 % on the cutting table. Just imagine, if you cut the fabrics without relaxing them you may end up getting your garments undersized on the tension it was given prior. 

Air freight calculation system for Garments

For air shipment, air freight charged or calculation system is depends on both actual weight and cargo weight. If the actual weight is higher than cargo weight, then airline will charge air freight based on higher weight that means they will charge on actual weight of the goods. On the other hand, if the cargo weight is higher than actual weight, then airline will charge based on higher weight, that means cargo’s weight.

For high density goods, the airline has decided to charge the heavy merchandise based on weight, and for low density goods the airline has decided to charge the low merchandise based on volume. As we know, airplanes can take less weight than ocean lines. Airline set the standard, when garment industry or manufacturer ship the goods by air, there is 70% chance to be charged based on weight and about 30% chance to be charged based on volume.

If your merchandise is of high density (heavy) such as jeans, flat packed shirt, jackets without polyester padding, T-shirt without hanger, there is a good chance you will be charged by weight. In that case, it is not possible to save air freight by packing the goods tighter in cartons to reduce the measurements.

However, if your merchandise is of low density (light weight) such as stands up collar shirts, shirts individually boxed, jackets with polyester padding, or down fill T-shirt or other shirts with hangers’ heavy gauge sweaters, there is a good change you will be charged by volume. In that case, you should make an effort to necessary to do so, you must know the following relationship between weight and volume as set by IATA (The International Air Transport Association)

1. In the South East to the U.S. destinations and Canada, most shipping locations used 1kg = 7000 cubic cm
2. In the South East to the U.S. destinations and Canada, certain shipping locations used 1kg = 6000 cubic cm

Therefore, when you have low density (light weight) goods to ship by air, in order to determine if you should try to make the cartons as small as possible to save freight, you should check the following:

First of all, you check with local air forwarding agent by asking him in the country where you are, how many cubic cm is considered 1kg in weight. He will tell you either 7000 cubic cm or 6000 cubic cm. After getting the answer you physically check the weight and measurement of the goods packed for air shipment. Now we have the below answers, as follows for example:

1. The country is Bangladesh and formula is 6000 cubic cm = 1kg
2. The measurement of the carton is 50 cm X 60 cm X 40 cm
3. The gross weight of the cartons is 16kg / carton

Now let us find out if we should try to make the cartons smaller to save air freight by doing the following calculation:

50 cm X 60 cm X 40 cm = 120,000 cubic cm

120,000 cubic cm divided by 6000 cubic cm = 20 kg

Now you know, by volume, the one carton is of 20 kg, but by actual weight, the carton is of only 16 kg. You also know the airline will charge whichever is higher, in this case, the will charge you for 20 kg by volume. If the air freight rate is 2.70 /kg, this carton will cost you $54.

Now, in order to save some money, let us try to make the carton smaller (usually by cutting down the height of the carton). Let’s say we have succeeded in cutting down the height by 5cm and see how much money we can save:

Original size of the carton: 50 cm X 60 cm X 40 cm = 20 kg

Now cut down to: 50 cm X 60 cm X 35 cm

50 cm X 60 cm X 35 cm = 105,000 cubic cm

105,000 cubic cm divided by 6000 = 17.5 kg

Now, by using the new carton, we have saved 2.5 kg and this carton will cost you only $47.25 (17.5 kg x 2.70= $47.25)

Should we try to cut it down further if possible?

The answer is yes, because 17.5 kg is still bigger than the actual weight. We should try to cut it down to:

50 cm X 60 cm X 32 cm

= 96000 cubic cm

= 96000 cubic cm divided by 6000

= 16 kg

Which is the same as the actual weight. In this case you will have to pay 16kg x 2.70 = $ 43.2 for the air freight of this carton no matter by weight or by volume the airline charges you.  Now you can see, by cutting the height down by only 8 cm, you have reduced the freight from $54 to $43.2, saving 10.80 / carton.

Since the saving is so great, should we try to cut down the height further? The answer is no, please see the following:

If we cut it down further by another 2cm, this will happen:

50 x 60 x 30 cm divided by 6000 = 15 kg

The airline will not charge you for 15kg, they will still charge you for 16kg because the actual weight is 16 kg, the last 2cm you cut down will not save you any money. However, if you can cut down the size of the carton and not hurt the appearance of the garments inside, you should always do it because over-sized cartons can easily be crashed due to insufficient support from inside, and in the season when air space is tight, your volumetric cargo may have lower priority than other people’s density cargo to get on the plane.

One point noteworthy is when you know it is going to be volumetric cargo and that the merchandise is sweater, for example, which can be squeezed without being hurt, you should use very strong carton to pack these goods such as 9 ply cartons (in some countries called 4-ply).

In that case, the airline would take the measurements from the biggest point to the biggest point. As a result, you will be charged more than you calculated. However, if you use stronger cartons you can avoid this to an extent. You should not worry about the 9 ply carton being heavier than the 7 ply carton to cost you more air freight, because you are being charged by volume, not by weight.