Stencils - When printing fine or reversed images, it is very important to use a low Rz (smooth) stencil such as CPS Ultra Cap EZ to minimise saw toothed edges. To get the very best results, low Rz should also be combined with a low EOM (stencil profile) which will minimise ink build at the image edge. The low Rz/EOM of CPS Ultra Cap HD controlled profile capillary films makes this the ideal product for solvent based inks.
When printing less complex images, a high quality dual-cure direct emulsion such as CPS Ultra Coat 535 is ideal, or if a one pot emulsion is preferred, then use CPS Ultra Coat 900.
Printing - If high opacity is required for the final flood coat colour, then it is better to print two thin layers rather than one thick layer. It is imperative that all the solvents are removed from the ink film during drying to give the best inter-layer adhesion. Note: Do not use retarders in the inks as these are difficult to dry out and will cause adhesion problems.
Be careful when overprinting trap colours as 24μ is the maximum total ink thickness recommended. Thicker ink layers will suffer from poor adhesion. Note: Always print Windotex and Fototex lacquers before printing the graphics layer to prevent ‘airing off’ adhesion problems.
How to minimise dust contamination
Dust is impossible to remove from the dried print, therefore prevention is always better than contamination!- Remove any contamination from the dry screen prior to printing with a low tack roller
Drying: Solvent based inks dry more slowly when printed onto Polyester as there is no absorption of the solvents into the film layer. As complete drying is critical to achieve good adhesion, jet air dryers are the recommended drying process due to the large air movement. Typical drying temperatures are: Zone 1: 70°C, Zone 2: 90°C, however temperatures as high as 100°C can be tolerated due to the stability of the Polyester substrate.
IR drying and rack drying are not recommended due to the low air movement and difficulty in removing all the solvents from the inks.
Ink cleaning On Press: If the screen needs to be cleaned during printing use CPS Screen Opener 511 or CPS Screen Cleaner K3x and allow the mesh to dry out completely before recommencing printing.
Ink cleaning Archiving: If the screen is to be archived for reuse, it can be cleaned with CPS Screen Opener 511 (Flash point 44°C), CPS Screen Cleaner K3x (Flash point 43°C) or CPS Screen Cleaner Vx (Flash point 63°C), paying particular attention not to damage the stencil.
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Name: William Shorter
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