In his presentation to delegates at the inaugural Inkjet Conference USA, Global Graphics Software’s CTO Martin Bailey will outline how software can solve problems that have been thought of up to now as addressable only in “hardware”. He points specifically to the role of halftone screens in avoiding mottle and streaking on printed output by controlling ink coalescence, and to how software is effective in correcting non-uniformity across the web.
“If your press is producing an orange peel effect”, he observes, “the temptation is to think that it can be fixed with inter station pinning or corona treatment to increase ink adhesion. Taking this action may reduce tonal mottle but it increases color mottle. If you try to solve the problem with Under Color Removal or Grey Component Replacement it reduces tonal mottle but increases graininess. The good news is that the orange peel effect can be corrected with a halftone with specially designed characteristics without increasing color mottle, noise or grain.”
Halftone screens create an optical illusion depending on how you place the dots. Having worked with vendors across at least a dozen inkjet presses Global Graphics Software’s engineers realized that the common denominator is the substrate used. The result is the recently released Advanced Inkjet Screens™: The Pearl screen produces a very natural effect on more or less absorbent substrates, whereas the Mirror screen is ideal for non-absorbent and poorly-wetting surfaces such as tin cans and flexible packaging, and also areas of dense metallic ink.
Advanced Inkjet Screens have been found to be effective with all the major inkjet printheads and combinations of electronics at any device resolution with any ink technology and with lots of different media.
Software is also effective in correcting non-uniformity across the web that may be caused by variation within a head, pressure or voltage changes or head wear, and results in a ‘smile’ shape.
“The temptation is to think that you can fix that by tuning voltages,” comments Bailey. “But not all heads have sufficient adjustment points to correct the smile and it can be difficult in overlap/stitching regions. There are other disadvantages too. Adjusting voltages reduces jetting stability and causes ink pressure and timing/drop speed variation. This increases the randomness of ink coalescence on the substrate, which causes texture artifacts. Now where have I heard that before?!”