Industrial & Specialty Printing - November/December 2012 - 14

Figure 4 Back printing

Figure 5 (Top) Clock Figure 6 (Bottom) Clock backlit with light on

aged during the printing process. It is important to take the same readings and measurements after each color layer. An overlay will sometimes require a combination of front- and back-printing. When this is the case, production will usually start with printing on the front, in the same order, with the back masked. After the front is printed and dried, it should be masked for protection. The back masking is then removed and printing resumes. Varying specifications in color and brightness requirements means the color-matching process must continue throughout the printing process. Readings for daytime and nighttime colors should be taken after each pass to ensure the desired color is reached. Visually evaluate colors during the production run and at the end of the curing line for any color drift. More testIng At this point, samples are submitted to the customer for final approval and will go through an approval process. The color has to be approved by a second source to verify that it matches their desired colors and shades. It will also go through testing for yellowing, fade resistance, alcohol resistance, water immersion, and more. It can sometimes take a year just for the colors to be qualified for the job. Once colors, printing, and the overlay are submitted and approved, you can finally move on to the next step: printing the overlays. Because there are so many levels of detail involved with each layer of color, you need to follow the same process used throughout the entire printing run. Rigid procedures for printing should be in place to ensure that you have a consistent product from run to run. Nothing can change once the process is set and validated by the customer. possIble Issues As with any highly detailed screen-printing project, there are many opportunities for something to go wrong. You need to pay careful attention to every aspect of printing to prevent defects or errors. A few common issues include: Contamination There are many variables that can cause contamination in your final product. Whether it’s dust particles in the air—or even hair—anything that can show up, even very slightly in ink, will result in a defective part that you’ll have to scrap and reprint. 14 | IndustrIal + specIalt y prIntIng www.industrial-printing.net

Scratching It’s important that your printed gauges be protected from scratches and other possible damage. Use masking to prevent any damage to printing or textures. Pinholes Printing bleed is necessary to make sure that all areas are covered with the customer-outlined color requirements, whether transparent or opaque. If your background is black or the opaque color, it also must be printing perfectly. If there are any holes or spots missed, they will only be accentuated when the gauge is backlit during nighttime driving, and the part will be rejected. Bad ink Old or expired ink can result in a poor end product. Because the approval process for color matching can sometimes take a very long time, the original ink used may no longer be available, or it may have slightly changed. It is important that inks used when you begin printing the overlays are the same, in every aspect, as the original approved process. You cannot permit any deviation. Delamination This is a big concern in any screen-printed overlay. Normally, delamination can be caused by under-curing inks. Allow 24 hours of post-curing before you apply a pressure-sensitive adhesive when using UV inks. Any number of reasons can cause delamination, including using the wrong ink. Adhere the instrument panel to the sub panel or instrument cluster and remove it after 72 hours, paying attention to any ink that comes off. When drivers look at the instrument panel on a vehicle’s dash, they probably have no idea about the time and engineering that goes into printing the display. Printing automotive instrument panels is rarely a short and simple process. High levels of detail and specifications require printers to spend a lot of time to develop a successful process, which then must be followed rigidly. Only with accurate color matching, precise printing, and appropriate storage and protection is a high-quality, durable instrument panel possible.

GM Nameplate

MIke McdanIel

Mike McDaniel is a member of the SGIA Printed and Electronics and Membrane Switch Council, the SGIA Industrial Applications Committee, and a judge for SGIA Golden Image Awards. He served as SGIA chairman in 2003. Mike has been with GM Nameplate for 36 years, where he currently works as the technical printing manager. In his position, he assists in the development of new technical-printing and regulated-products projects, working closely with engineering and quality departments.

Industrial & Specialty Printing - November/December 2012

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