Session 4 Printing 1
Introduction Dyeing in localised, patterned design Uses same colourants as in dyeing Print paste is thickened* (with starches or gums) to prevent wicking or flowing of print design * final viscosity: 5,000 20,000 cp (centipoise) (ref: USP 4826504); the upper limit is determined by fabric flatness while the lower limit depends on the process and sharp printed marks obtained. Institute of Textiles and Clothing 2
Comparison of Dyeing & Printing Printing has greater scope for design More colours can be achieved in printing Complicated designs produced by printing Printing costs less Institute of Textiles and Clothing 3
Textile Printing Market Annual production: 25 billion m 2 6000 printers: rotary screen 61%, flat bed 23% Average colour numbers per design: 7 Institute of Textiles and Clothing 4
Current Situations More designs & colours Shorter length of run Quick turnaround time Price pressure Customization Institute of Textiles and Clothing 5
Methods of Printing Screen printing Rotary-screen printing Heat-transfer printing Digital printing Institute of Textiles and Clothing 6
Screen Printing Screen preparation Fine mesh screen (polyester or nylon) fabric selected Screen fabric mounted on wooden or metal frame Photosensitive chemical applied on screen Design transferred to screen Institute of Textiles and Clothing 7
Printing Screen Printing Screen in close contact with fabric Print paste poured on screen Print paste forced through mesh with squeegee Colourant fixation Printed colourants fixed with heat or steam Institute of Textiles and Clothing 8
Institute of Textiles and Clothing 9 9
Toile Du Juoy Screen Printed Using Vat Dyes 10 Institute of Textiles and Clothing 10
Hand Screen Print Drapery 11 Institute of Textiles and Clothing 11
Screen Printing Characteristics Low capital investment Suitable for large design but not continuous design Low productivity but flexible can be automatic or manual Institute of Textiles and Clothing 12
Rotary-screen Printing Screen preparation Design transferred to screen with laser Printing Continuous rotation of screen while in contact with fabric Print paste fed into inside of screen Print paste forced through mesh with stationary squeegee Colorant fixation Institute of Textiles and Clothing 13
Rotary-screen Printing Characteristics Resembles automatic flat-bed printing except with cylindrical printing screens High printing speed Screens are nickel (light-weight) Continuous printing method Institute of Textiles and Clothing 14
Rotary-screen Printing Characteristics Institute of Textiles and Clothing 15
Institute of Textiles and Clothing 16
Heat-transfer Printing Design printed on paper (transfer paper) which is stored until ready for use When fabric is ready to be printed, printed transfer paper in contact with fabric with heat application No further treatment required Institute of Textiles and Clothing 17
Ink-jet Printing It is a system in which droplets of ink are ejected onto a surface to form patterns Ink-jet printing includes creation of ink stream or droplets under pressure ejection of ink from a nozzle orifice control of droplet size and uniformity Institute of Textiles and Clothing 18
Ink-jet Printing control of which drops reach the substrate placement of drops on the recording surface Institute of Textiles and Clothing 19
A Piezo Ink Jet System Institute of Textiles and Clothing 20
Commercial Inkjet Printer Institute of Textiles and Clothing 21
Printing Method Comparison Rotary Flatbed Digital Print Speed 2500 meters/hour 600 meters/hour 20 meters/hour Applications Pigment Pigment Pigment Reactive Reactive Reactive Acid Acid Acid Disperse Disperse Disperse Vat Vat Substrates All possible products All possible products Limited in fibre type (e.g. blends) IT integration +/- +/- ++ Qualities 50-195 mesh* up to 400 mesh depending on printing device *mesh = number of threads per inche Institute of Textiles and Clothing 22
Types of Prints Direct prints Discharge prints Resist prints Institute of Textiles and Clothing 23
Direct Prints Design printed directly on white or coloured cloth (the latter is called overprint) Institute of Textiles and Clothing 24
Overprint face (Piece dyed, then design is printed) 25 Institute of Textiles and Clothing 25
Overprint back (Piece dyed, then design is printed) 26 Institute of Textiles and Clothing 26
Discharge Prints Print paste contains colour-destroying chemicals (normally reduction agents). When design printed on coloured fabric, colourants originally on fabric are destroyed (removed) Institute of Textiles and Clothing 27
Discharge Print 28 Institute of Textiles and Clothing 28
Resist Prints 1. Pattered design printed on a white fabric with chemicals which resist dye penetration 2. Piece-dye the fabric Institute of Textiles and Clothing 29
Batik 30 Institute of Textiles and Clothing 30