Sanforizing Machine and Process
The machine used for the sanforizing process is called “Sanforizing Machine”. Sanforizing Machine means a machine consisting of a large steam-heated cylinder, an endless, thick, woolen felt blanket which is in close contact with the cylinder for most of its perimeter, and an electrically heated shoe which presses the cloth against the blanket while the latter is in a stretched condition as it curves around feed-in roll.
Sanforizing is a mechanical finishing process of treating textile fabrics to prevent the normal dimensional alternation of warp and weft. It is also called anti-shrinkage finishing process. It is a process of treatment used for cotton fabrics mainly and also for some other textiles made from natural and synthetic fibres. It is a method of stretching, shrinking and fixing the woven cloth in both length and width, before cutting and producing to reduce the shrinkage which would otherwise occur after wash.
- Sanforizing process is based on the principle that when an elastic felt blanket is passed around a metal roller in contact with it, its outer surface is process extended and the inner surface contracted. So the process is called controlled compressive shrinkage process.
- The process of sanforizing includes the stretching and manipulation of the fabric before it is washed.
- During the sanforization process, the fabric is fed into a sanforizing machine where it is treated with water or steam to promote shrinkage, then pressed against a heated rubber band to relax and re-contract the fibers.
- The amount of potential wash shrinkage must be determined prior to shrinking. A full width sample is wash-tested according to the test method. After the lengthwise and width wise shrinkage has been determined, the compressive shrinkage machine can be adjusted accordingly.
- The cloth is continually fed into the sanforizing machine and therein moistened with either water or steam. A rotating cylinder presses a rubber sleeve against another, heated, rotating cylinder. Thereby the sleeve briefly gets compressed and laterally expanded, afterwards relaxing to its normal thickness. The cloth to be treated is transported between rubber sleeve and heated cylinder and is forced to follow this brief compression and lateral expansion, and relaxation. It thus gets shrunk.
- The greater the pressure applied to the rubber sleeve, the bigger the shrinking afterwards. The process may be repeated.
The process of Sanforizing can be described by the following schematic below:
- Fabric (F) passes through the skyer (S) or other moistening device and is moistened by water and/or steam. This will lubricate the fibers and promote shrink ability within the fabric.
- Fabric is moistened in such a way that every single thread achieves a moisture content of approximately 15%.
- Above step allows compression of the fabric with very little resistance.
- When the fabric passes through the clip expander (C), we obtain the required width. The clip expander also transports the fabric to the most important part of the machine: the rubber belt unit (indicated by arrows in above figure).
- In the close-up of above figure, we see the endless rubber belt (R). By squeezing rubber belt (R) between pressure roll (P) and rubber belt cylinder (RB), we obtain an elastically stretching of the rubber belt surface.
- The more we squeeze the rubber belt, the more the surface is stretched. This point of squeezing is known as the pressure zone, or the nip point.
- Fabric (F) is now fed into the pressure zone.
- When leaving the pressure zone, the rubber belt recovers itself and the surface returns to its original length carrying the fabric with it. The effect of this action is a shorting of the warp yarn which packs the filling yarns closer together. At this actual moment, shrinkage occurs.
- After compaction within the rubber belt unit, the fabric enters the dryer (D). Here the fibers are locked in their shrunken state by removing the moisture from the fabric.
- After the compressive shrinkage process is completed, another sample of the fabric is taken. This sample is also wash-tested. The final result of this test must meet the Sanforized Standard, in length and width before it may carry the Sanforized label.
- All Sanforized Licensees are contractually obligated to follow the required test method and meet the standards set forth by The Sanforized Company.
Sanforizing Machine Parts
This machine consist of the below mention parts.
- Entry / Exit J-box
- Infeed roll
- Rubber Belt
- Felt drum
- Felt centering unit
- Delivery roll
- Machine Safety switches
Entry / Exit J-box:
This unit is used to unroll the fabric and store it in to the Scray to run the machine continuously. It is consist of a motor controlled by the inverter, compensator and expender rollers.
The speed of the motor can be controlled by the inverter and compensator is used to synchronize this unit with the machine. During the running of machine, press the push button “J-box filling” the speed of J-box drives is increased and J-box will be filled. When we depress the push button “J-box filling”, the speed of J-box down to stoppage.
If the minimal fabric contents are falling, the speed of the J-box drive increases the machine speed with the influence of the compensator and breaking roll is released.
We can also see the speed of J-box on the meter at operating panel.
There is a photo cell installed at the J-box which sense the fabric indicate that the J-box contain the fabric or not.
Inlet roll transfer the fabric from J-box to rubber belt. It is consist of motor, inverter and compensator. The speed of the motor synchronized with the machine rubber belt.
This is a main part of the machine. It is consist of the heavy motor, inverter, safety limit switches. To run this motor we first select the rubber belt and then press the ON push button. The speed of the belt motor is increased or decreased by the push buttons at operating panel. The speed of the machine is shown on display at operating panel. There are the a safety limit switches installed at both sides ( left & Right). If the belt cross the right or left limits then limit switch is activated and machine will stopped to protect the belt.
It is consist of a motor, inverter, felt centering device, safety limit switches and compensator. The motor speed controlled by the inverter and synchronized with the help of compensator. The speed of the felt depend on the speed of the rubber belt.
To control the shrinkage of the fabric, there is a shrinkage meter and by the adjustment of this POT we achieved the required shrinkage and we can see it on digital meter in term of percentage. Also the analog ammeter is installed at the operating panel which shows the tension current. There is an additional option by which we can bypass the compensator with help of the selector switch at operating panel in case of overfeeding process. To protect the felt for any damage, there are two limit switches installed on both sides (left & right).
Felt centering device:
To control the movement of the felt there is a centering guide roller which changes it position with the help of guiding motor. This motor is controlled by the limit switches which sense the felt position and makes the contact to run the guiding motor clock wise and counter clock wise, according to the position.
This unit gets the fabric from the exit J-box and passes it to the winder or plaiter. It is consist of a motor, inverter and hand POT. The selector switch is used to select it at operating panel and other exit operating panel. The speed of the roll is synchronized to the rubber belt.
Plaiter / Winder:
This unit coupled with the delivery roll with the help of chain and clutch. There are separate clutch for the plaiter and winder. The selector switch for the plaiter and winder in placed at the exit operating panel. Both clutches are operated with the 24VDC power supply.
Rubber Belt Grinding unit
This unit is installed before the rubber belt and used for the grinding of the rubber belt. The motor is coupled with the grinding roll by the gears. This is a single speed motor and power connection is in star-delta fashion. The controlling panel of grinding unit is installed near the rubber belt and we can turn it ON and OFF from the selector switch at this panel.
All the inverters communicate with each other with the help of CAN communication system. There is a CAN communication system installed in the electrical panel which control the speed of the machine, shrinkage percentage and inverter frequencies control.