Start Here October '20

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73 S T A R T H E R E 2 0 2 0 Figure 7 UV printer for this project, the largest concern is for proper functioning of the printer and print head. The best way to check this is to run a nozzle check on the printer to ensure that all print head nozzles are function- ing and firing properly. Most printers print a pattern of ink lines that make it simple to identify any problems with the print head. It is also a good idea to check the ink levels of all the ink colors to make sure there is a sufficient amount of ink needed for the job. Depending on the UV ink chemistry and the intended use of the sign, a metal adhesion promoter may or may not be needed to help improve the adhesion strength of the ink to the metal surface. We use a metal adhesion promoter for this project. The promoter used here is Bohle Verifix. Other metal promoters such as Supply 55 AP3155 can also be used. The technique for applying adhe- sion promoter is important. If too little promoter is used, the higher adhesion strength may not be realized. If too much promoter is used, the promoter may be overly saturated and may not cure prop- erly under the ink layer. High promoter saturation can prevent proper bonding of the ink to the metal surface. As a general rule, I advise customers to wear nitrile gloves when handling adhesion promoter. Using a clean ultra-microfiber lint-free cloth, dab a quarter-sized amount of promoter onto the cloth. Wipe the pro- moter in a circular pattern over the entire metal surface, similar to washing a window (Figures 1.1 and 1.2). The next step is key to adhesion pro- moter success. Flip the cloth over to a dry spot and rub the metal surface again. This helps remove any excess promoter left on the metal surface. The metal surface may appear completely dry or slightly wet or greasy. The appearance of the promoted surface may vary depending on the adhe- sion promoter type and chemistry. Regardless of the promoter's appear- ance, it is most important that the surface appear uniform across its entirety. At this point, the adhesion promoter has done most of its job by creating a higher molecu- larly receptive metal surface ready to bond to the printed UV ink. The next step is to open the artwork for the sign and make any necessary adjust- ments for print production. This project involves three individual print passes, each using a different print mode. Figure 2 illustrates the first pass, which is a flat print using a white with color print mode.

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