Objectives of sanforizing machine, structure and working principle of sanforizing machine
Requirement of fabric sanforizing process:
When the fabric passes through the various dyeing process, it goes under moderate tension. The fabric length gets elongated during various dyeing processes. If we use the fabric directly coming from the dyeing process, it has a lot of residual shrinkage in the warp and weft directions. If the fabric having much residual shrinkage is used to make garments and other items, the big dimensional change occurs after washing the products. Most of the time, this dimensional change goes beyond the acceptable limit. We need to fix this problem before cutting the garment or any other items. Sometimes two different fabrics are used in the same garment. If both fabrics have differential shrinkage, the puckering effect gets appeared on the garments. Thus the residual shrinkage is a very big problem in the fabric. This is the reason why does the sanforizing process of the fabric is required.
Objectives of sanforizing (zero-zero) process:
The objectives of the sanforizing or zero-zero process are:
* To minimize the after washing fabric shrinkage.
* To improve the dimensional stability of the fabric.
* To soften the fabric handle.
* To increase the fabric GSM.
* To increase the fabric cover in the fabric.
The sanforizing is a fabric finishing process. It is a pre-shrinking of the fabric by passing the fabric into a rubber unit. The ends and picks of the fabric come closer to each other after the sanforizing process. When the threads come together to each other, the thread to thread gap or air space in the fabric gets reduced. The reduced air space in the fabric results in the form of improved fabric dimensional stability. This process is also called sanforization.
When the fabric is washed, laundered, ironed, or dry cleaned, the negative change in the fabric dimensions is called fabric shrinkage. This residual shrinkage is controlled by the sanforizing process.
Effect of sanforization(zero-zero) finish:
PASSAGE OF FABRIC IN SANFORIZING MACHINE:
Structure and working principle of sanforizing or zero-zero machine:
The main parts and their functions of the sanforizing machine are given below:
The inlet J-scray is used to store the fabric during the batch change. This Inlet unit consists of various parts like tension rolls, draw cylinder, pressure roll and break roll. Tension roll regulates the tension of the fabric getting feed during the process. The draw roll pulls the fabric and feeds it to the machine. The important function of the above unit is to feed the fabric evenly throughout the machine.
Damping Cylinder or steaming drum:
The damping cylinder provides intensive, uniform and controlled steaming of the fabric. when the fabric passes through this damping cylinder, the fabric absorbs the moisture and get moist. The damping cylinder has a steam-heated inner shell. This inner shell gets surrounded by a steam permeable wire mesh. A mangle cloth is wrapped in several layers around the wire mesh. The damping cylinder is heated from the inside with saturated steam.
Mahlo device (weft straightener):
The main function of this unit is to eliminate the bowing of the fabric being processed. This device contains two bow and three skew rollers. This device corrects the skewness and Bowness present in the fabric being processed and straightens the weft yarns present in the fabric.
Damping Unit or rubber blanket shrinkage unit:
It is the most important unit of the machine. The main function of the rubber blanket shrinkage unit is to help to allow the warpwise shrinkage to the fabric. It consists of a rubber heating cylinder, endless rubber, pressure roll and tension roll. A stainless steel cylinder, which has a micro-polished surface that ensures minimum friction between fabric and cylinder so that the fabric is free to follow the movement of the rubber.
Principle of applying shrinkage on fabric:
Hot cylinder (A), thick rubber, fabric (B) Rubber unit Actual view of rubber unit
Fabric is passed between the hot cylinder and endless rubber. The heating of the cylinder takes place by steaming arrangements. Pressure is applied on the fabric between the rubber and cylinder by pressure roll. During this above operation, shrinkage takes place on the fabric.
Squeeze rolls squeeze away extra water from rubber after water spray.
During drying of fabric in the felt unit, the moisture is uniformly absorbed from the fabric by the felt blanket and the shrinkage of the fabric is set. This unit is also has a felt drying cylinder, which dries the endless felt cover.
This cylinder is used to further cool the fabric to normal temperature.
Batching and plaiting unit:
This unit winds the fabric on a frame or plaits the finished fabric in a suitable box/ trolley. Outlet J-scray Felting unit Batching Arm Exit plaiter arrangement
Operation sequence of sanforizing or zero-zero finishing machines:
* The main panel power supply is switched on. the steam valve is opened.
* The fabric passage without a crease is ensured.
* The proper water spray in the rubber unit is ensured and the tension is adjusted while the machine running.
* The final width, shrinkage and defects are checked in the fabric.
* The main power is switched on and then the compressed air is opened. the water valve and steam are also opened at the same time.
* The rubber unit and felt unit condensate line is checked while starting the machine.
* The fabric is transported to the inlet feeding unit of the sanforizing machine. a hydraulic hand puller or electric truck is used for fabric transportation.
* One end of the fabric getting processed is stitched with the other one leader fabric in the machine and the straightness of fabric stitching line (seam) without a crease is ensured.
* The fabric is observed before and during the process. if any defect is found, it is reported to the concerned person immediately.
* The speed of the machine is set according to the fabric quality. 50-100 metres/minute speed is used for normal finishing operation. it varies depending upon the fabric quality.
* The lightweight fabrics are processed at a higher speed and heavyweight fabrics are processed at a slower speed,
* Weft straightener (Mahlo) is kept ‘ON’. the warp and weft patterns in the fabric straightness are checked visually.
* Selvedge folds and improper feeding of fabric in the inlet of the machine are not allowed.
* The temperature of the rubber unit is kept 90-120 degrees C and the felt unit temperature is kept between135-150 degrees C. the temperature range varies according to the fabric quality.
* The residual fabric shrinkage is checked before processing, the required shrinkage value is set in the control computer accordingly.
* If the set shrinkage and actual shrinkage differs, then the proper grinding on the endless rubber is done according to the machine manufacturer instructions,
* The fabric width on the plaiter is checked frequently and the fabric tension is adjusted according to requirements by changing tensioner roll pressure.
* The actual shrinkage of the fabric is checked in the machine outlet by shrinkage scale. the required moisture content in the outlet fabric is maintained.
* Finished fabric is checked for fabric defects like stains, dust, chemicals, rust, handling mark, stains mark, crease mark, water dropping, oil marks, and grease marks, etc.
* If the machine stops for a long time, the leader fabric is to be put on the machine and the rubber unit is to be cooled immediately without delay.
Cleaning in sanforizing(zero-zero) finishing machines:
* The accumulated dust and dirt are removed regularly from the machine.
* All the rollers are cleaned with dry fabric whenever required.
* The rubber unit, water spray unit and felting unit are cleaned at regular intervals.
* The inlet sensors and fabric guides are cleaned properly.
v * All the wastes are collected properly and are stored at the designated place.
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