Mechanical Cleaning Process of Fabrics

Mechanical Cleaning:
Mechanical cleaning processes are viable alternatives to traditional solvent-based cleaning operations. They reduce waste production and eliminate potential safety problems with the handling and usage of toxic, ozone-depleting, and often-flammable solvents. Mechanical cleaning operations are such as sanding, grinding, polishing, brushing/sueding, cropping and shearing. Mechanical cleaning avoids the use of toxic or dangerous chemicals by substituting mechanical work for chemical work. 
Brushing process of fabric
The pre-cleaning of grey fabrics may be carried out in a separate unit just before cropping and shearing operations. The efficiency of pre-cleaning is the foundation of good cropping and shearing. The pre-cleaning operation is achieved with :
  1. Thorough grinding of the cloth surface by emery covered rollers.
  2. Scraping with suitable designed and located scraping blades.
  3. Efficient brushing on both sides of the cloth.
With the progress of grinding and scraping action, the cloth surface gets covered with thread ends, dust, fluff, dirt etc., thus the pre-cleaning unit should have a good dust exhausting system. Mechanical cleaning processes offer a wide range of cleaning and surface preparation options to solvent cleaning.

The purpose of brushing/sueding is to remove the short and loose fibres from the surface of the cloth. It also removes husk particles clinging to the cloth. Brushing is mainly done to fabrics of staple fibre content, as filament yams usually do not have loose fibre ends. Cylinders covered with fine bristles rotate over the fabric, pick up loose fibres, and pull them away by either gravity or vacuum. The raised fibre ends are cut off during shearing operation. Brushing before cropping minimise pilling.

Cropping and shearing:

Shearing is an operation consists of cutting the loose strands of fibres from either surface of a fabric with a sharp edged razor or scissors. By manipulating the shearing it is also possible to cut designs into pile fabrics. Good cropping is perhaps, the simplest way of reducing the tendency of blended fabrics to 'pill'. In the case of cotton fabrics, in particular, care should be taken to see that the shearing blades do not scratch the surface of the fabric, which otherwise can cause dyeing defects during subsequent dyeing.

The term 'cutting point' denotes the contact line between the spiral shearing cylinder and the ledger blade, over which the fabric has to pass during cropping and shearing operation. Each cutter is provided with adjustable ledger blade. Before leaving the machine, the cloth is brushed by a spiral revolving brush. The machines are of totally enclosed construction with exhaust channels. Although there have been no major changes in the latest cropping and shearing machines, a modem fully automatic shearing range has the following features :
  1. Fabric feeding device (electronically controlled) ensuring the entry of crease free fabric.
  2. A soft bed under the cutters so that the blades which cut the fibres close to the surface do not damage the fibres in the yam.
  3. Seam joint sensors (electronic) which lift the shearing rolls away from the fabric surface when a seam passes.
  4. Magnetic metal detectors sense the iron particles embedded with the cloth and activate the limiting switch, so that the machine stops, the concerned particles are removed and the machine restarted.
  5. Hydraulic speed gear system has been replaced by suitable DC drives. Modem shearing machine can operate up to a speed of 100m/min. The units have been made more modular, in order to facilitate quick installation.
Shearing machines fitted with serrated blades have been found satisfactory forthe cutting of polyester materials. Polyester staple fibre fabrics are cropped and singed mainly to control the pilling tendency. For polyester/wool blended fibre fabrics a good cropping is essential if the fabric is not to be milled. If it is desired to finish simulating wool, loose polyester should first be removed by brushing, cropping and singeing and then the fabric is soap-milled to produce a wool cover, which can be cropped to give the required appearance and handle.

  1. Chemical Technology in the Pre-Treatment Processes of Textiles by S.R. KARMAKAR
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia.

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