Why we switched to A lasered pad printing plate?
Since the beginning of 2017, Printing International has completely switched over to laser-based CTP technology for the production of pad printing plates (clichés). CTP stands for computer-to-plate, CTP allows the digital images to be engraved directly on the pad printing plate by means of a laser, without an intermediate step via photographic films, exposure system, development, retouching and etching.
This technology offers several advantages compared to the production of the pad printing plates by means of films and etching:
- better quality of the laser pad printing plate
- more stable halftone images
- more screens can be combined
- sharper edges of the printing images
- less labor intensive; fewer steps are required to a perfect record.
This technology is also much better for the environment:
- there is no more water consumption
- the use of chemicals, such as developer, fixer and etching product are no longer necessary because the film development is superfluous; the silver also disappears from the wastewater. This means that we can also speak of a chemical-free CTP.
With this technique, various cost savings occur, such as:
- reduced water consumption
- no film development step
- reduced waste costs
- fewer service contracts for equipment
With the traditional technology, 15 steps are needed to achieve an etched steel pad printing plate, while with CTP technology, only 4 steps are needed to achieve a lasered pad printing plate. The more steps, the more variables and the more inaccuracies (deviations) can occur.
Short pulse or long pulse laser?
Printing International uses a short pulse laser for engraving the steel pad printing laser plates. The classic laser (long pulse) applications are based on the principle of very fast local heating, melting and evaporation of the base material. This inevitably results in undesirable side effects such as burrs, recrystallization and micro-cracks. These effects lead to poor deterioration of the printing plate and damage to the doctor blade, which is detrimental to the printing quality. A short pulse laser provides sufficient energy that is very suitable to eliminate these side effects, so that a higher quality is delivered. Due to the high beam quality of the laser, a spot size in focus of around 15 microns can be achieved. High precision XY axes are also used, which guarantees an accuracy of +/- 4 microns.
Thanks to our highly advanced laser and RIP software, we ensure the perfect screened pad printing laser plate. RIP stands for Raster Image Processor. The function of a RIP is to convert files from prepress, such as Post-script and PDF, to raster image data, usually high resolution (up to 2400 dpi), halftone images and monochrome bitmaps, and thereafter the data is offered to the laser as output. Different lineatures can be combined, up to 200 lpi for halftone and CMYK images and up to 300 lpi for support screen. It is also possible to adjust the screen percentages; here we will correct the point reduction and point enlargement that occur during printing by means of a pressure characteristic curve. To determine the pressure characteristic curve, a raster grey stage is printed with multiple raster values. These values are measured with a densitometer. The values obtained are then plotted in a diagram, these values are compared with the original values, a point transfer curve is created from this, this curve is then used to draw up the pressure characteristic curve. This curve only applies to the combination of printing ink, product, pad printing pad and pad printer for which it was composed. If the same product is printed on a different machine, with a different pad printing ink or with a different pad printing pad, then this will always result in a different pressure characteristic curve. Drawing up this curve with the classic technology of plate manufacturing is practically impossible due to the many steps and variables in the production process. We also offer the possibility to use trapping in your multi-colour images.
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