Tuesday, January 11, 2022

Objectives of hot air stenter machine, structure and working principle of a hot air stenter machine

Hot air stenter machine:

A stenter machine is used in the wet processing of the fabrics. It is a multi-purpose wet processing machine.

The main objectives and uses of a hot air stenter machine are given below:

* The main objective of a hot air stenter machine is to dry the processed fabric.

* To apply the finishing chemicals to the fabric.

* To pad the fabric with a pigment colour.

* To recover the fabric width shrunk in the dyeing process.

* To improve the dimensional stability of the fabrics.

* To cure the pigment printed fabrics.

* To make the structure of the synthetic fabrics by the heat-setting process.

* To rectify the bowing or skewing present in the fabric. 

    

  Structure and Working principle of stenter machine: 

  The structure and working principle of a hot air stenter machine are given below: 

    Inlet J-scray:

* This is the fabric feeding unit. 

* The fabric enters into the machine from this point. 

* The fabric batch or fabric trolley is placed behind the inlet J-scray unit. 

* The fabric is stored in the J-scary when the empty fabric batch or trolley is replaced with the new fabric batch or trolley. 

* The j-scray avoids the machine stoppage during batch or trolley change.  the Inlet unit consists of a tension device, draw roll, pressure roll and break roll. 

* The tension roller provides the required feeding tension to the fabric.  

* The important functions of the above rollers are to feed the fabric evenly throughout the machine.


Padding mangle: 

* Next, the fabric enters into the padding and squeezing unit.

* The padding unit consists of the finishing chemical trough and padding roller. 

* Almost half of the bottom side of the padding roller gets dipped in the finishing chemical solution. 

* When the fabric passes over this roller, the fabric and roller dip together in the finishing chemical solution. 

* The finishing chemicals are being applied to the fabric in the padding unit. 

* Now, the fabric has a lot of moisture in it. 

* If the excess amount of water is not removed the drying of it takes much time in the drying chamber. 

* The drying speed gets decreased and the drying cost gets increased. 

* When the fabric passes between the nips of squeezing mangles, the excess amount of water gets eliminated from the fabric.



Mahlo device (weft straightener): 

* This is an electronically controlled device. 

* It has two bow rollers, three skew rollers, sensors, and a control computer unit. 

* When the fabric enters into this unit, it observes the straightness of the weft yarn ( picks) present in the fabric continuously. 

* When it detects bowing or skewing in the fabric, the sensor sends a command to the control computer immediately. 

* The control computer activates the bow and skews rollers.

* The bowing rollers rectify the bowing present in the middle of the fabric and the skewing rollers correct the skewing present in the sides of the fabric. 

* This device gets more important when check fabrics are processed in the stenter machine.


Fabric Over-feed system:

* The main objective of the fabric over-feed unit is to control the after washing shrinkage and to improve the dimensional stability of the fabric being processed. 

* If the fabric feeding speed ( metres/minute) is more than the endless chain speed ( meters/minute), the fabric shrinkage during drying takes place. 

* The overfed length of the fabric is gripped by clips or pins mounted on the endless chain track at both sides of the machine. 

* The fabric gets gripped on the clips or pin in such a way that lengthwise puckering of the fabric appears during fabric overfeeding. 

* The lengthwise fabric shrinkage occurs during fabric drying. Thus the after washing shrinkage or dimensional stability of the fabric gets improved. 

* The fabric can be stretched up to 2-3 inches with the help of clips or pins. 

* If the fabric is fed loosely in the width direction, the widthwise shrinkage is achieved after drying. 

Endless chains, pins & clip arrangement:

* The hot air stenter machine consists of two endless chains. 

* These endless chains travel over the chain track. 

* One chain is mounted at one side of the machine and another chain is mounted on the other side of the machine.

* Either clips or pins are mounted on each endless chain.

* These clips or pins hold the fabric selvedge firmly. 

* Nylon fibres brushes are mounted at each side of the endless chain at the entry of the fabric. 

* These brushes press the fabric selvedge just opposite of pins. 

* It helps to penetrate the pin in the fabric selvedge. 

* The chain track gets automatically lubricated during machine operations. 

* The endless chain size varies according to the number of drying chambers present in the stenter machine. 

* Normally, each endless chain gets 40-60 meters long. The fabric can be stretched up to 2-3 inches with the help of clips or pins.


Outlet chain track: 

* The main function of the outlet chain track is to help the de-pinning or de-clipping of fabric from pins/clips. 

* It also cleans the clips and pins properly. 

Drying chambers:

* The main function of the drying chamber is to dry the fabric or to fix the finishing chemicals with hot air from the blowers. 

* The blower sucks hot air from the radiator and blows it into the nozzles. 

* The hot air coming out from nozzles dry the fabric. 

* The air is heated with the help of the oil circulating in the oil pipes at a very high temperature. 

* The oil is heated with the help of the thermo-pack. 

* The drying chamber also contains a width adjustment spindle and pin/clip chain track inside the drying chamber. 

* There are 8-10 drying chambers in the stenter machine, each having 3 meters in length. 

Batching and plaiting

 unit: 

* When the dried fabric comes out of the machine, it is either wound on the batch or folded by a plaiter. 

* The batching unit consists of the batching roller and pneumatic cylinders. 

* A cloth roller mounted over the iron frame is placed under the batching roller. 

* When the batching roller rotates, the cloth roller also rotates due to the surface contact of the batching roller. 

* Thus, the fabric gets wound on the cloth roller. 

* If a plaiter is used, the folded fabric is collected in the cloth trolley.

The hot air stenter machine speed depends upon the fabric quality and the number of drying chambers used in the machine.

Please click on the below video link to watch the full lecture in Hindi:


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