Improving the stability of small dots is a key area in flexo printing. Beside the techniques focusing on the 2D geometry of the highlight screen dots (flexo optimized hybrid screenings, uniform shape for the smallest screen dot), there are techniques for changing the 3D shape of a small dot even on CTP systems which only allow 1-bit TIFF input.
The idea is that the power of the CTP laser can be modulated digitally just like in a switch-mode power supply: any laser power level can be achieved by changing the full-on and full-off states quickly enough – and even if the laser is quick enough to follow the quick changes, the emitted energy will be averaged on the surface of the photopolymer.
Using this technique, the area around a small dot can be exposed by a reduced laser power in order to create a “shoulder” around the dot – an area with increased height which supports the dot, preventing it from breaking or bending.
In the 1-bit TIFF file this will appear as a “cloud” of pixels around the dot. Operators can use the patterns brought by StudioRIP, or can define their own patterns as BMP files, while the radius of the pattern can be dynamically reduced as the dot increases using an interpolated table defining the radius on various halftone percentages (StudioRIP will only apply the dots which fall within the defined radius for the given halftone percentage).
Finally, to keep the dot shape stable, there is a “safety area” between the dot and the pixel cloud, a gap of user definable size which will prevent the pixels of the cloud to distort the dot.
The new feature is available in the Dot shoulder tab of the Screening type settings dialog. Note that the result is only visible in the Test screen window and the final TIFF file, but StudioRIP’s preview system will hide it for smoother user experience.
