PRINTING TECHNOLOGY

Offset Printing: A Color Blindness Test For Printers : This is a color blindness test.  Though these pictures can tell you if you suffer from color blindness, it should not replace an actual diag...

Offset Printing: Troubleshooting Piling Problems : For the past few weeks we've had serious problems within piling on our four color web press.  We are running four units in the following o...

Offset Printing: Troubleshooting Piling Problems : For the past few weeks we've had serious problems within piling on our four color web press.  We are running four units in the following o... 

Printing Inks Ink Ingredients Ink ingredients fall into three main categories: pigment, vehicle, and modifiers/additives. Because there are so many different types of printing processes and print applications, the ingredients used in these three categories may vary widely. For example, for offset lithography, ink requires a higher degree of pigment than many other processes. This is because nearly half of the ink used in the offset process does not reach the printing surface. In direct printing methods, such as letterpress, a much higher percentage of the ink reaches the substrate. Pigment The ingredients that comprise the color of the ink are referred to as pigment. The pigments are formulated from substances that create a desired color when the substances are blended together in specific proportions. Some of these substances may be ingredients found in nature or they may be produced synthetically. The substances can be in the form of dyes, powders, liquid dispersions, or concentra...

• Printing inks dry by different mechanisms depending on the printing method.• The common methods are penetration (absorption), oxidation, setting, evaporation and polymerization. Normally the drying is a combination of above mentioned methods. • How the ink dries by different printing methods: Sheet-fed offset : : By oxidation and absorption Heatset: : By evaporation of solvent . Offset/UV-ink : Polymerization Gravure: evaporation Flexo: evaporation Drying of the Ink – Sheet-Fed Offset Printing • Sheet-fed offset inks dry by oxidation and by absorption. The ink pigment is dispersed in medium that is a mixture of oil and resin (resin dissolved into oil). The resin stays on the top of the printing ink layer and covers the surface of oxidized oil. The solvent of printing ink penetrates into the paperboard pores. The resin hardens and the surface of printed layer gets touch resistant. After the ink has set the oxidation and further on drying can begin. The ink layer gets harder and...

Preventive quality control is before-the-fact action utilizing quality control procedures to prevent problems before they occur and thus minimize downtime and waste. Quality control procedures are succesful when they are in sync with maintenance planning, continuous productivity improvement programs and business align ment strategies. Total Production – and Prepress – Maintenance (TPM) concepts integrate with those of Preventive Maintenance (PM) and Total Quality Management (TQM), aiming at zero breakdowns. Apart from any formal certification program, print consistency can largely be obtained by adherence to standards as defined in the ISO 12647, “Graphic technology – Process control for the production of half-tone colour separations, proof and production prints”. 1. Viewing Conditions The pressroom’s light levels must be high enough around the press to permit press crew to install plates, blankets and packing easily and to make press adjustments without eye strain. Having a light shi...

PRESSMAN TIPS  Packing and cylinder pressure seem to be the number one culprit in printing related problems. It is absolutely necessary for the press operator to check and maintain proper printing pressure between plate, blanket, and impression cylinders. Press manufacturers should be able to supply this valuable infor mation. Most of the time the packing information is located on a plate on the press or in the operating manual. How much pressure is too much? Most operators feel that is .004" squeeze is good, then .008" must be better, and if that doesn't work then an extra .002" - .004" will certainly help. This will without a doubt effect quality and production. Most presses should operate with .004" - .006" squeeze between cylinders. Any more than this can cause problems like dot gain, emulsification, bearing shock marks (streaks), poor register and fit to name a few. It would take several paragraphs to explain how each one of these problems ...