In flexo, it is general practice not to use traditional offset angles such as CMYK 15°–75°–90°–45°. This is because the use of engraved anilox rolls to deliver ink to flexo plates introduces an additional potential for patterning due to screen angle interference. Instead of traditional offset angles, flexo typically uses shifted or 7.5° angles. A typical flexo angle set might be CMYK 67.5°–7.5°–82.5°–37.5°.
Traditional offset angles are not supported on ThermoFlex devices. ThermoFlex imaging ablates the carbon mask attached to the flexo media. The ablation process blasts particles of carbon out of the mask, and these particles must be removed by the debris removal system. Even with a powerful laser and an effective debris removal system, there are always microscopic debris trails left between the swaths of the imaging beams or diodes. The debris trails are oriented at 0°, and can produce visible interference with line screens produced at 0° or 90°. For this reason, ThermoFlex devices are not qualified for running line screens at traditional offset angles, because yellow is typically required to be imaged at either 0° or 90°.
See Also