Weft Knitting Calculations
• Weft Knitting Calculations

In flat and circular knitting machines, the number of needles, machine division, machine diameter, machine fineness, fabric width and working speeds are calculated. In all knitting machines, the number of needles is the most important factor affecting the width of the knitted fabric. Since a needle corresponds to a loop, the number of loops also gives us the number of needles. Total Needle Count in Flat Knitting Machines

When calculating the total number of needles in flat knitting machines, the machine working width in inches (inches) and the machine fineness (E) (Fein) are needed as seen below.

*** working width; is the distance between the first needle and the last needle on the flat knitting machine needle plate. working width It is given in imperial units of measure in inches or cm. However, in calculating the total number of needles, the working width of the machine is taken as inches.

*** Machine fineness (fein) (E); is the number of needles per 1 inch (2.54 cm) on the needle plate. Total number of needles in single plate flat knitting machines

TIS = MCE x E

TIS: Total number of needles

MÇE : Machine working width (inch)

E : Machine thickness (inch)

Total number of needles in double plate flat knitting machines

In double plate weft knitting machines, there are as many needles on the back plate as there are needles on the front plate. Therefore, the total number of needles in a plate is multiplied by 2. Total Needle Count in Circular Knitting Machines

While calculating the number of needles in circular knitting machines, the machine diameter (pus) is used because the needle plate of the machine is cylindrical instead of the working width in flat knitting machines. The machine diameter is calculated in inches, just like the working width on flat knitting machines.

*** Machine diameter (haze); is the diameter of the cylinder needle plate in circular knitting machines. Although the machine diameter is stated as haze, the unit of measurement is inches.

Total number of needles in single plate circular knitting machines

TIS = Q x π x E

Q: Machine diameter (haze)

3.14: π Constant number

E : Machine fineness (Fein)

Total number of needles in double plate circular knitting machines

Since there are needles in the cover needle plate as well as the number of cylinder plate needles, the total number of needles in a single plate is multiplied by 2.

Machine Fineness and Scale Calculations *** Machine fineness (fein) (E)

It is the number of needles per 1 inch on the same needle plate on flat and circular knitting machines. It is denoted by the letter E and read as fain. The international unit of measurement, the inch, is equivalent to 2,54 cm (25,4 mm).

In knitting machines, there is a relationship between the machine fineness and the yarn thicknesses that can be used in the machine. As the machine fineness increases, the yarn fineness also increases. The thread should be suitable for the fineness of the machine. If a thick thread is given, the needle hook will break, and if a thinner thread is given than it should be, gaps form between the loops and it will have the appearance of a net.

Relationship between machine fineness (E) and yarn count (Ne) The higher the fineness of the machine, the finer the weave to be obtained from this machine.

Relationship between machine fineness (E) and needle count

The higher the machine fineness (E), the greater the number of needles.

Needle selection should be suitable for machine fineness, otherwise undesirable faults will be observed in the fabric.

Machine scale (t)

It is the distance between two adjacent needles on the same needle plate in flat and circular knitting machines. It is denoted by t, its unit is mm.

P = Needle pitch

t = N+P (Distance between two needles) Fabric Width and Fabric Shrinkage Calculations

Fabric width is the value in cm of the distance from one edge of the fabric to the other. The fabric width can be adjusted to the desired extent, not being larger than the working width in flat knitting machines. Since the needle is fixed and the shuttle is moving in flat knitting machines, the needle can be canceled and the needle can be operated for the desired width. This is not possible with circular knitting machines. The main factor that determines the fabric width in these machines is the machine diameter. Because in circular knitting machines, the needles are movable and the shuttle is fixed. Even if you cancel the needle on the circular knitting machine, it knits that part as a skipping knit because it is movable.

Considerations when measuring knitted fabric width

Measuring should not be done as soon as the fabric comes out of the machine. Because the fabric was stretched during production and is in a different state from its actual dimensions.

For this reason, the fabric should be rested for a while after leaving the machine, and then the measurement should be made by considering the following points.

The measurement process should be done where there are no wrinkles in the knitted fabric.

While measuring, the fabric should neither be stretched nor the pot should be left, it should be made from the normal-looking part of the fabric.

The measurement process is made several times from different parts of the fabric, the deviations are determined by taking the average.

The measurement should be made from neither the head nor the last part of the fabric ball. The midpoints of the fabric ball should be preferred as the machine does not get the desired speed when the machine is first started and when the machine is stopped.

Fabric Width in Flat Knitting (Knitwear) Machines It can be worked in the desired width and range in flat knitting (knitwear) machines. In these machines, the width of the widest fabric that can be worked is calculated in the calculation of the fabric width.

MCE = TIS x 2.54 / M

MÇE : Machine Working Width (cm)

TIS: Total Number of Needles

E : Machine Fineness

The total number of needles used here is the total number of needles in the single-plate flat knitting (knitwear) machine calculation because the fabric width does not change in single and double-plate, only the surface of the fabric changes. Therefore, the number of needles in a single plate is taken. The working width of the machine also indicates the highest width that the knitted fabric can take on the calculated machine. Fabric Width for Circular Knitting Machines

When calculating the fabric width in the circular knitting machine, first the total number of needles is found and the result is divided by the number of loop bars per 1 cm on the knitted fabric.

L = Q (R) x 3.14 x L / D/cm

L : Fabric Width (cm)

Q (R) : Machine Diameter (Haze)

3.14 : π constant number

E : Machine Fineness (Fein)

D/cm : Bar density

Rod frequency; The number of loops in 1 cm is called (D/cm).

Factors Affecting Fabric Width in Knitted Fabrics

Machine Diameter or Machine Working Width: It is the diameter of the circle formed by the cylinder needles in circular knitting machines. It is the distance of any needle in the cylinder circle to the needle opposite it. The machine diameter determines the maximum fabric width that can be knitted. It is possible to obtain wider fabric as the machine diameter increases.

In flat knitting machines, the working width determines the width of the fabric. If the working width of the machine is 2,50 meters, it is not possible to knit more than this size in this machine.

It is possible to produce fabrics of various widths with a slight difference from the machine with the same diameter in a circular knitting machine, so fabric production depends on:

>>> Knitting pattern

>>> Fabric weight, stitch length adjustment, stitch density

>>> Finishing operations

Machine Fineness and Total Needle Count

The machine fineness (E) and the total number of needles in the machine affect the width of the knitted fabric. In flat and circular knitting machines, the machine thickness determines the number of loop bars per cm on the fabric. For example, when the measurement is made on the fabric produced in two machines with the same working width but different thickness, the number of mays per cm will be different. The width of the fabric knitted on a thinner machine will be wider than the other fabric. Since the total number of needles is based on the number of needles working in flat knitting machines, it does not affect the fabric width in circular knitting machines as much as it does in flat knitting machines.

Knitting Type and Pattern Structure

In circular and flat knitting machines, the density or looseness of the knitting and the structure of the patterns affect the width of the fabric. The width of the loosely knitted fabric will be wider when knitted tight in one machine and loose knit in the other in two machines with the same characteristics. In addition, some patterns cause the fabric to gather or open. In particular, stacked knits collect the fabric more and have a transverse effect.

Loop Bar Frequency

Loop bar frequency; The number of loops in 1 cm is called. The change in the number of loops is very important, it is directly proportional to the fineness of the machine, if the fineness increases, the number of needles increases, if the number of needles increases, the number of loops (bars) increases, if the fineness decreases, the number of loops (bars) decreases.

The loop bar density of two different fabrics produced by adjusting the density setting on the same machine will also be different. When the other properties are the same, the fabric with less bar density will be wider than the other.

Not every type of thread is suitable for working on the machine, it is necessary to choose the thread number suitable for the fineness of the machine and the fineness of the needle. As the thread thickness increases, the fabric width increases to a certain extent. This is due to the texture of the fabric, because the thickness of the thread is proportional to the fineness of the machine. Since the thick yarn is knitted on machines with a lower gauge, the knitting will be looser and the fabric will also have an effect on the width.

Working Speeds in Knitting Machines

Working speed of knitting machines is important to increase efficiency in production. Flat knitting machines and circular knitting machines are very different in terms of speed due to their working principles.

Working Speeds of Flat Knitting Machines

Flat knitting machines are slower as they are round-trip. Flat knitting (knitwear) machines are separated from each other in a 1-2-3-4 system. The number of systems here indicates how many rows the machine knits in one round trip. Each system creates a queue.

Working speeds of single system flat knitting (Knitwear) machines

In flat knitting machines, apart from the working width of the machine, there are also sled return paths on both sides. When calculating the machine operating speed, these return paths should also be taken into account. When making the calculation, the result including the return path as the machine width should be taken as a basis. The value found here reveals the speed of the sled (saddle) to which the systems of the flat knitting machine are connected, in proportion to the number of systems it makes per second.

V (m/sec.) = ME xn(course/min.) / 100

ME = MCE + (2xDY)

DY : Return path (cm) (sum of parts not worked on the machine)

ME : Slideway (machine width) (cm)

V : Machine speed (m/sec.)

n : Number of round trips made by the machine in one minute

In flat knitting machines, the number of revolutions is given instead of the number of courses. Therefore, when calculating, it should be taken into account that the machine makes one round trip and one return and knits two rows in one revolution. That's why we multiply the number of revolutions by two when finding the number of rows.

Örnek

The working width of the single system flat knitting (knitwear) machine is 320, the return path is 40 cm, and the machine speed is 16 rpm. What is the working speed of this machine?

V (m/sec.) = ME xn (course/min.) / 100 x 60

ME = 320 + (40x2) = 400 cm

Since the sled covers the return path once on the way and on the way back, the return path is multiplied by two when calculating the width of the machine.

n = 16 (rpm) x 2 = 32 strokes/min.

V (m/s) = 400 x 32 / 100 x 60

V (m/sec.) = 2.13 m/sec.

Working speeds of flat knitting (knitwear) machines with double and more systems

The difference of flat knitting (knitwear) machines with double or more systems from single system is that if each system knits a row, it knits as many rows as the number of systems in each movement. Here only the number of rows changes. In the example calculated for a system above, the machine is 32 courses/min. According to the example above, the number of revolutions was 16 rpm. The only system machine with 32 courses/min. was happening. In machines with more than one system, the number of revolutions is multiplied by the number of systems, and the number of rows per minute (course/min.) is found. For example; According to the above data, the machine is 16 rpm. and if the machine system number is 6, the calculation is as follows.

V (m/sec.) = ME xn (course/min.) / 100 x 60

ME = 320 + (40x2) = 400 cm

n = 16 (rpm) x 2 = 32 strokes/min. 32x6= 192 courses/min for one system.

V (m/s) = 400 x 192 / 100 x 60

V (m/sec.) = 12,8 m/sec.

In the flat knitting machines seen above, the number of systems is as important as the number of revolutions in terms of production efficiency.

Working Speeds of Circular Knitting Machines

Circular knitting machines are many times faster than flat knitting (knitwear) machines. The number of revolutions and systems in circular knitting machines is much higher than in a flat knitting machine. The main purpose and working principle of circular machines is to produce more fabric in a short time. The systems are fixed and movable needle plates are formed so that it is designed to knit 40-120 rows at the same time. Working speeds in circular knitting machines are calculated with the following formula:

V (m/s) = π xnx Q (Haze) x 2.54 / 100 x 60

The number 2,54 in the formula is to convert this value to cm because the machine haze is given in inches. The speed calculated in circular knitting machines shows the value in meters of the distance made by the knitting cylinder per second. In circular knitting machines, the n value, that is, the revolution/minute, is used as it is given. Because these machines rotate circularly in the same direction, when they reach the starting point, it is calculated as one revolution. If a machine is 28 rpm. If it is showing, this means that the machine is turning 28 revolutions per minute.

V : Machine Speed ​​(m/sec.)

π : 3.14 constant number

Q : Machine Diameter (haze)

n : Machine speed (rpm)

Örnek

The speed of the mbie machine with a diameter of 30 pus is 29 rpm?

V (m/s) = π xnx Q (Haze) x 2.54 / 100 x 60

V (m/s.) = 3,14 x 29 x 30 x 2.54 / 100 x 60

V (m/sec.) = 1,15 m/sec.

Due to the working principle of circular knitting machines, the number of systems has no effect on the peripheral speed.

Posted by %PM, 09% 559% 2016 15%:%Apr in Knitting