What is Roller Printing?
Roller Printing also called cylinder printing or machine printing or engrave roller printing. It is a modern continuous printing technique. In this method, a heavy copper cylinder (roller) is engraved with the print design by carving the design into the copper. Roller printing is a continuous automatic production in which the process is carried out with the aid of engraved copper rollers. A separate engraved roller is used for each colour. Due to low productivity, roller printing method has been almost completely replaced by rotary screen printing.
In the past, the design was engraved by hand, but this was found to be unreliable and time consuming. Nowadays, the photographic engraving method, together with the chemical (mainly strong acids) etching technique, is the widely used approach. The size of the print repeat is governed by the printing machine and the size of the roller. Most machines accommodate rollers with a maximum 16-inch circumference which means the size of the print repeat cannot be larger than 16 inches. The roller width varies from 30 to 80 inches and is normally wider than the fabric to be printed. The numbers of colours within a print repeat are limited by the numbers of rollers that the machine can accommodate.
Common Faults or Defects of Roller Printing
Major defects of roller printing are briefly described below:
Scratches:
Gritty particles in colour paste cutting the surface of the roller deeply enough to show them when printed.
Snappers:
Loose threads from the cloth escaping under the lint doctor, bits of the dried up paste and other hard particles cause snappers, which are large double stripes of colour running along the length of the cloth. Normally two stripes of colour with a white centre are seen.
Lifts:
These are also called as minute snappers, occurring usually at regular intervals, which are normally caused by some hard particles like a metal piece getting embedded in the engraving of the roller and protruding from it, thereby lifting the Doctor blade temporarily.
Streaks:
Fine lines parallel to the selvedge may be caused due to scratches on the engraved roller or a cut on the colour doctor edge because of some grit in the colour paste.
Scumming:
Soiling of the cloth by one or more colours due to insufficient scrapping of the print paste from the engraved portion. It may be due to rough doctor blade, improper adjustment of doctor blade, badly faced roller or defective printing paste preparation.
Scrimp:
Creases remaining in the cloth while printing give rise to the defect of non-printing underneath the fold.
Uneven printing:
Uneven pressure due to faulty lapping or improper feed of the print paste, too much polishing of certain parts to eliminate scratches, give uneven impressions.
Lobbying:
This is an uneven printing due to slippage of roller round its mandrel, due to improper fitting.
Back-grey crease:
Improper feeding of the fresh back grey or due to heavy soiling, inefficient washing and improper drying of used back-grey are the main reasons for this defect.
Back grey stitch impressions:
Although this is an inevitable defect because of the stitch impressions, it can be minimised by using the suitable sewing thread.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
