Calendering Machine for Textile: Parts and Types

Calendering Machine for Textile:
The calender is a series of hard pressure rollers used to form or smooth a sheet of material. Calendering finishing is a process of imparting luster and smoothness to a fabric by passing it between pressurized rollers. If the moist fabric is passed through the pressurized rollers, the calendered fabric will be quite similar to steam ironed fabric. Main effects produced by calendering include reduction in fabric thickness, compaction of weave structure, change in fabric handle, change in fabric luster. Variation in any of the following parameters results in different effects produced by calendering: fiber content, fabric construction, moisture in the fabric before calendering, any chemical finishing applied before calendering, temperature of calender roll(s), relative speeds of fabric and rolls, roll composition and configuration, pressure applied and number of times the fabric is passed through the calender rolls. One of the calender roll is usually made of stainless steel (which may be heated to the required temperature) while the other may be covered with highly compressed cotton, paper or synthetic material. Common types of calendering machine used in the textile industry include: 3-roll friction calenders, Schreiner calenders and embossing calenders.

Calendering Finishing Process
Figure 1: Calendering Finishing Process

The use of calendering machine to produce flat, compact and polished fabric is very still popular. From the beginning of fabric manufacturing, it was observed that the application of pressure by a simple iron or press could alter the properties of fabric. The alteration in properties depends on the ability of the fabric to be mechanically changed.

Calendering Machine
Figure 2: Calendering Machine

The use of calendering machine is an important technique in finishing of cotton, linen rayon and silk materials. On the other hand, synthetic fibers react to mechanical deformation, but they require the presence of heat to defeat the physical and thermal memory of the fibers. The object of normal calendering is to flatten yarns, to close interlacements in fabric and to impart a lustrous, smooth feel to the fabric.

Different Components / Parts of Calendering Machine:
Normal parts of a calendering machine for textile are as follows

  1. Winder
  2. Metal detector
  3. Seam detector
  4. Rollers (cotton, reclon and steel)
  5. Anti static rod
  6. Oscillating roll
  7. Batcher sensor
  8. Cooling drum

A short description of each calendering machine parts are given below:

1. Seam detector: Function of seam detector is to bypass the seam.

2. Metal detector: Metal detector to detect metal partials.

3. Anti static rod: Anti static rod is used to remove static charges.

4. Small winder: When we have to calendar short width fabric and we can also run short width fabric with long width fabric.

5. Oscillating roll: To avoid selvedge overlapping on batcher.

6. Cotton roll: For soft finish the fabric is passed through cotton bowl. This roller is made up of cotton.

7. Steel roll: To give smoothness and luster. The temperature is provided to steel roller about 32-200°C with help of electric heater as we increase the temperature shining will increases only used for cotton CVC and percale and PC.

8. Reclon roll: When fabric passes through Reclon roll and steel roll giving smooth and luster effect is generated. When it runs with steel roll and reclon roll and cotton roll dull effect is generated. When it runs b/w steel and reclon gloss effect is generated.

9. Cooling drum: Cool down the fabric water circulates inside the cooling drum.

Types of Calendering Machine:
Several different finishes can be achieved through the calendering process by varying different parts. The main types of finishes are beetling, watered, embossing, Schreiner, swizzing and so forth.

There are nine types of calender finishing machine:

  1. Friction calendaring machine
  2. Schreiner calender
  3. Nipco-Flex calender
  4. Felt calender
  5. Embossing calender
  6. Swizzing or swissing finish
  7. Chasing finish
  8. Moiré calender
  9. Ciré calender

Above types of calendering machine are described below:

1. Friction calendaring machine:
In friction calender, plain calender rollers are used with hot metallic roller in the entry, synthetic roller in the middle and cooling roller at the delivery. Friction calendering gives a higher gloss and a greater closing of the yarns; it is produced by bringing the cloth into contact with a three-bowl process consisting of a heated bowl, a polishing bowl and a chilled-iron bowl which is travelling at a faster speed than the cloth itself.

The machine is composed of a soft roll in the middle and two hard rollers on both the sides. The surface speed of the friction roll is faster than the soft roll, ensuring gloss appearance of fabric due to the friction between them. This also remarkably reduces the gap between threads or fibres. The speed ratio between friction roll and fabric can reach 1.2:1. For the friction roll, the friction range can be changed and the temperature usually is from 100 to 160°C.

Advantages:

  • Produce more smooth, glossy and higher lustrous appearance
  • Remove crease and wrinkles
  • Reduce fabric thickness
  • Heavy close up of threads
  • Suitable for finishing of highly glazed linings, prints etc.

2. Schreiner calender:
A silk-like appearance, especially with mercerized fabric, is achieved by passing over a metal bowl with engraved inclined lines (i.e. angles with warp or weft) of about 125–500/in. under very high pressure (about 10 tons). Schreinering is an inexpensive way of producing a very high degree of lustre in cotton fabrics. In order to obtain a silk-like luster, it is necessary to produce a very large number of small reflecting surfaces distributed in several planes. The production of luster by the Schreiner finish is therefore a method of embossing.

Though friction calender can produce lustrous, smooth and drapeable fabric, it gives a papery thin handle. Schreinering is a special type of embossing where a heated metal roller engraved with fine diagonal lines comes in contact with the fabric and presses those fine lines into its surface.

A typical Schreiner calender has strong frames carrying two bowls (7.5 cm in diameter) the top one being of special, fine-grained steel, which is engraved with the required number of lines and is heated by gas. The bearings of the top bowl are cooled by water.

Schreiner calender
Figure 3: Schreiner calender

Advantage:

  • Gives silk like appearance to cotton

3. Nipco-Flex calender:
The pressure application concept of this calender is different from the conventional calendering system. The pressing roller consists of a rotating shell that is covered with a highly elastic plastic material named as RACOLAN. The roller has fixed axels on which hydrostatic support elements are mounted that press the racolan shell against either steel or a cotton/paper roller. The hydrostatic pressure is applied with oil and is adjustable according to width of the cloth. The NIPCO roller can be arranged in vertical position or in L shape with a hot steel roller at top and a cotton bowl in front of it.

The main advantages of NIPCO calender over a conventional calender are;

  • Attainment of very high pressure.
  • Adjustment of pressure line according to width of cloth.
  • No over load at the fabric selvedge.
  • Easy installation and removal of the rollers.

4. Felt calender:
Felt calenders are mainly used for imparting luster and smoothness to silk, rayon and cotton knitwear materials. These work at low pressure and temperature than used for cotton. The cloth is pressed between an endless felt blanket and a hot steel cylinder at a speed of 20 to 40 meters/minutes. By adjusting speeds of the feed and take up rollers the tubular knitwear can be compacted to some extent on this calender.

5. Embossing calender:
Embossing is a particular calendering process through which a simple pattern can be engraved on the cloth. An embossing calender usually consists of two bowls; the top metal bowl is engraved with a suitable design and the softer composition bowl has a surface that accepts the embossing pattern. Embossing produces a raised relief design which is permanent on thermoplastic fiber but temporary on cotton.

Calendering rollers for embossing effect
Figure 4: Calendering rollers for embossing effect

Embossing calender is similar to the Schreiner calender, but the bowls of this calender are much bigger (38–45 cm in diameter).

Advantages:

  • Crepe or pebble effect is produced
  • Produce temporary or permanent effect
  • It is cheap due to smaller metallic bowl

6. Swizzing or swissing finish:
Swissing finishes are obtained merely by passing the cloth, suitably conditioned, through the nips of a calender in which the surface speed of all the bowls is the same; the cloth is then batched or plaited as required. A smooth appearance is thus obtained according to the number and composition of the bowls.

7. Chasing finish:
It is similar with swizzing calender. The fabric is passed through the nips of the calender, over the external rollers and back into the bottom nip of the calender. Multiple layers of fabric run through the nip resulting in a thready appearance with soft handle. This is mostly done for linen fabric.

8. Moiré calender:
Moire aims at production of wave-shaped moire effects (so-called soaking), which occurs due to partial even printing of weft ribs on viscose and silk fabrics. In moiré finishing, the roller is engraved with a watermark or wood grain pattern. The moiré effect resembles a watermarking effect; it is produced when the weave structure of a tightly woven fabric is distorted by the movement of very fine yarns due to surface pressure. This is possible only if the fiber being treated is capable of deform.

The moiré style is in demand for cotton and dyed synthetic fibers used for curtains and wall coverings. Acetate and viscose fibers are more capable of showing the moiré effect than other fibers.

9. Ciré calender:
Ciréing provides a highly polished surface to fabric, making it appear wet. The friction roller runs faster than that in the case of friction finishing. The ciré calender is used for glazing and glossing fabric surfaces using a high temperature of 220°C and pressure as high as 1500 PLI. Some porosity reduction and compaction is also obtained through this process. All types of fabrics can be processed, but they are usually made of 100% synthetic fibers or high 75% synthetic fiber content blends

References:

  1. Principles of Textile Finishing by Asim Kumar Roy Choudhury
  2. Handbook of Value Addition Processes for Fabrics By B. Purushothama
  3. Advances in the Dyeing and Finishing of Technical Textiles Edited by M. L. Gulrajani
  4. Reference Book of Finishing By Pietro Bellini, Ferruccio Bonetti, Ester Franzetti, giuseppe Rosace, Sergio Vago
  5. Textile Finishing Edited by Derek Heywood
  6. A Novel Green Treatment for Textiles: Plasma Treatment as a Sustainable Technology By Chi-wai Kan
  7. Textile Engineering – An Introduction Edited by Yasir Nawab

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