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Printing & Color Matching
Printing: Graphic overlays, membrane switches, labels and nameplates can be printed using either screen printing of one of several digital printing technologies. Melrose can help you select the best printing option by identifying the tradeoff’s applicable to your part.
- Digital printing is increasingly in use because: 1) No added cost for extra colors, and fine gradients; 2) Need for quick turnaround
- Screen printing is best suited to
1. A color reference must be defined. The Pantone Matching System (PMS) is the most commonly used system for specifying a color standard. The pantone "swatch book" is readily available, can be inexpensively purchased and contains more than 1000 colors. A less common color system is the Federal Standard 595a..
Note: Pantone & Fed Std 595a Limitations: These color systems have two limitations. 1) If the swatch book is not new, colors may have faded, and may not be comparable to a new book, 2) The pantone system was developed for 1st surface printing of lithographic inks on white coated paper. Because inks used are screen printed on the second surface of a transparent material, or the material printed on is not a totally opaque white, a color shift is introduced by the transparent material on which the ink is printed.
2. Melrose Matches the Desired Color and Creates A Color Chip using the process and substrate material to be used in production. The preciseness of the match to a PMS color will be influenced by: 1) the substrate on which the color is printed, 2) the material through which the ink is viewed (if any), 3) the inks used, 4) characteristics of the full color process printing method (e.g., CMYK) employed to approximate a pms color match.
3. Comparing production parts to the standard: Once the customer has signed off on Melrose’s color match, color must be controlLED in production. In process control is achieved in one of two ways.
- Visual comparison in a controlLED light booth. Under most circumstances, a careful visual comparison of the color chip and the production part is sufficient to assure good color control. It is essential that this color check be done in a in a light booth that ensures a controlLED lighting environment (typically fluorescent lighting). However full daylight, variable daylight, incandescent can also be used for illumination in the light booth if those environments more closely duplicate the environment in which the part will be used.
- Instrumentation Comparison: Color difference in numerical terms can be determined using a spectrophotometer. Melrose uses a Minolta spectrophotometer to take numerical readings of color in the 3-D CIELAB color space. The spectrophotometer reads lightness, and chromaticity, reflecting those parameters as numerical values of L*, a*, b*. By comparing the 3D coordinates of a color chip to a production part the color difference can be determined. For more details on the CIELAB color space see this link: Colorimetry_photonics.pdf.
Color matching is a vital aspect of nameplate, graphic overlay, membrane switch and label manufacturing. Color must be defined on the first production run, then repeated reliably on reorders. Parts that are viewed side by side are often a color matching issues. Meeting these objectives requires special care. Three steps are involved.
Higher quantities, exact color matches, high opacity, bright colors, light shades of grey or brown, reflective or shinny metallic silver, gold and other colors.
- Screen and Digital printing combinations. Melrose can combine digital and screen processes to achieve the best of both technologies. For example, printing of multiple colors and gradients digitally, with 2nd step of screen printing metallics, exact pms matches, and opacity coats.
Membrane switch PET/silver circuits