Types of warp knitting m/c: Two major classes of warp knitting m/cs:- 1. Tricot warp knitting m/c 2. Raschel warp knitting m/c.Features Tricot warp knitting m/c:• In the past, tricot m/cs mainly employed bearded

needles with a pressure bar• Tricot m/cs have a gauge expressed in needle per

inch and chain link numbering 0, 1, 2, 3, 4 etc. generally with three links per course

• Their sinkers, which are joined to each other at the front and back, never move clear of the needles as they combine the functions of holding down, knocking over and supporting the fabric

• The fabric is drawn-away towards the batching roller almost at right angles to the needles bar.

• The warp beams are accommodated in an inclined arc towards the back of the m/c with the top beam supplying the front guide bar and the bottom beam supplying the back guide bar

• The warp sheets pass over the top of the guide bar rocker shaft to their tension rails situated at the front of the m/c

• Mechanical attention to the knitting elements is carried out at the front of the m/c, as the beams prevent across to the back.

• As all the warp sheets are drawn over the rocker shaft to the m/c, it is easier to thread up the guide bars commencing with the needle bar.

• The guide bars are therefore numbered from the back towards the front of the m/c because of threading sequence.

FeatureRachel warp knitting m/c: 1. Rachel m/cs used latch needles together with a wire or

blade 2. It has a gauge expressed in needles per 2inches

(5cm) so that for example a 36 gauge Rachel m/c will have 18npi

3. Their chain links are usually numbered in even numbers 0, 2, 4, ….etc generally with 2 links/course

4. Rachel sinkers only performs the function of holding down the loops whilst the needles rise

5. Rachel sinkers are not joined together by a lead across their ends nearest to the needle bars so they can move away clear of the needles towards the back of the m/c for the rest of the knitting cycle

6. The fabric is drawn downwards from the needles, almost parallel to the needle bar at an angle of 120°-160° by a series of take-down rollers.

7. The warp beams are arranged above the needle bar, centered over the rocker shaft, so that the warp sheets pass down to the guide bars on either side of it

8. The beams are placed above the m/cs so that it is accessible at the front for the fabric inspection

9. At least four 32″ diameter beams or large numbers of small diameter pattern bars

10. The guide bars are threaded, connecting with the middle bars and working outwards from the eitherside of the rockershaft

11. The guide bars are numbered from the front of the m/c

12. The needle trick plate acts as a fabric support ledge and knockover surface.

Difference between Tricot & Rachel warp knitting m/c: Tricot Raschel1. In the past, bearded needle was

used but now a days compound needle used

2. M/C gauge expressed in needle per inch

3. Chain link numbering 0, 1, 2, 3, ….etc

4. Function of sinker is holding down, knocking and supporting the fabric

5. The fabric is drawn away towards the batching roller almost at right angles to the needle bar

6. The warp beams are accommodated in an inclined towards the back of the m/c there the top

7. The warp sheets pass over the top of the guide bar rockershaft to their tension

8. Mechanical attention is carried out at the front of the m/c

9. The guide bars are numbered from the back towards the front of the m/c

10. High speed production

1. Rachel m/c used latch needle together with a wire or blade

2. M/C gauge expressed in needle/2inch

3. Chain link numbered in even numbers 0, 2, 4, ….etc

4. Sinker performs the function of holding down the loops whilst the needle rise

5. The fabric is drawn downwards from the needles almost parallel to the bar at an angle of 120°-160°

6. The warp beams are arranged above the needle bar centered over the rocker shaft

7. The warp sheets pass down the guide bar

8. Mechanical attention is carried out at the back of the m/c

9. The guide bars are numbered from front of the m/c

10.Low speed production

Tricot warp knitting M/C Rashel Warp knitting M/C

WEFT KNITTINGTypes of weft knitting m/c:According to the end product, the weft knitting m/c

may be broadly classified as either:– Fabric m/cs – Garment length m/cs

According to their frame design and needle bed arrangement, the weft knitting m/c may be broadly classified as either:

– Straight bar frame m/cs– Flat knitting m/cs – Circular knitting m/cs

Features of fabric m/cs:• Large diameter, circular, latch needle m/cs (also known

as yarn goods or piece goods) knit fabric, at high speed.

• The fabric is manually cut away from the m/c usually in roll form after a convenient length has been knitted.

• Most fabric is knitted on circular m/cs either single-cylinder (single jersey) or cylinder and dial (double jersey) of the revolving needle cylinder type, because of their high speed and productive efficiency

• Sinker wheel and loop wheel frames could knit high quality specialty fabrics with bearded needles although circular m/cs employing bearded needles are now absolute, the production rates of these m/cs were uncompetitive

• Unless used in tubular body-width, the fabric tube requires splitting into open-width

• The fabric is finished on continuous finishing equipment and is cut-and-sewn into garments or it is used for household and technical fabrics

• The productivity and patterning facilities of fabric m/cs vary considerably.

• Generally; cam settings and needle set-outs are not altered during the knitting of the fabric

Flat knitting m/c: Feature:• 2 stationary needle bed in flat knitting m/c arranged in an

inverted V formation • Latch needle is used• Angular cam of a bi-directional cam system used• There is a separate cam system for each needle bed• The two cam systems linked together by a bridge, which

passes across from one needle bed to the other• Carriage with determined yarn carrier issued • Cam system is attached to bottom side of carriage • The flat m/c is the most versatile of the weft knitting m/c• Fabric produce with finer to coarser yarn• The operation and supervision of the m/c is simple• The stitch length range is wide and possibly of changing the

m/c gauge• Trimmings, edging, collars, to shaped panels and integrally

knitted complex garments and other articles

Classification of circular knitting m/c:1. Circular bearded needle single-jersey fabric machine 2. Revolving cylinder latch needle machine3. Circular garment length machine1. Circular bearded needle single jersey fabric machine: Types of machines are divided into two types:-

a) Sinker wheel machine or French/Terrot type m/cb) Loop wheel frame or English type m/c

Both of them have the following common features:- Needles are fixed in a revolving circle on needle bed Knitting action is entirely achieved by ancillary elements moving yarn

and loops along the needle stem Here tubular fabric is knitted with its technical back facing outward Low productivity but has an ability to produce unusual and super-

quality knitted structures2. Revolving cylinder latch needle machine: There ate two main types of revolving cylinder latch needle machine,

namely- Open top or sinker top or single jersey m/c Cylinder & dial m/c or double-jersey mc/

05/01/23Md.Ahashan Habib B.Sc in Textile Engineering(DU)

Knitted Loop1. Knit Loop 2. Tuck Loop 3. Miss Loop

Tuck stitch: • A tuck stitch is composed of a held loop, one or more

tuck loops and knitted loops. • It is produced when a needle holding its loop also

receives the new loop which becomes a tuck loop, because it is not intermeshed through the old loop.

Miss/Float stitch: • A float stitch is composed of a held loop, one or more

float loops and knitted loops. It is produced when a needle holding its old loop fails to receive the new yarn that passes, as a float loop, to the back of the needle and to the reveres side of the resultant stitch.

• The miss stitch can occur accidentally as a fault due to incorrectly set yarn feeders.

Methods to obtain Tuck/Held loops:1. Without casting off operation in loop forming cycle , i.e.

Tucking of the latch2. Without clearing operation in loop forming cycle, i.e.

Tucking in the hook3. With switching a needle out of action from loop forming

cycleTucking on the latch: – When tuck stitch formation is performed without casting-off and

sinking are excluded from the loop formation cycle. In this case, the needles 4 and 7 knit the loops 3 and 6, while the needle 5 performs all the operations up to joining and stops. Then a new yarn 2 is fed in its hook and this will be the tuck loop, the old loop 1 remains on the closed latch and this will be the held loop.

– After the needle 5 is lifted for clearing, in the following loop formation cycle it receives a new yarn and knits a loop from it, casting-off upon it old held loop 1 and the tuck loop 2

– Step of forming held loop in 5 needle:

Difference between Warp knitting & Weft knitting.Warp Knitting Weft Knitting

• The loops are produced to the length of fabric

• The threads runs in the vertical direction

• Each loop in the horizontal direction is made from a different thread

• It is elastic to the length • It’s elasticity is less • Yarns are supplied from

beam • At least one yarn is

needed for each needle • Less shrinkage

• The loops are produced to the width of the fabric

• The threads runs in the horizontal direction

• A horizontal row of loops can be made by using on thread

• It is elastic to the width • Higher elasticity • From cone • Any number of needle

are required for on e yarn

• More/Higher shrinkage