FM Screen 30 microns highlight dots lost on CRON CTP

sornchai

Well-known member
Our prinect calibration manager create process calibration for 20 microns but I put 30 microns to used it printing on uncoated stock
Norminal 5,10,20,30,40,50,60,70,80,90,95
Process 11.6 / 22.2/ 40.9 / 55.7 / 68 / 77.3 / 84.7 / 90 / 94.3 / 97.4 / 98.8
Measured = same as process
problem is highlight dot always lost look like rubber delete pencil images on notes. Is it come from plate curves or CTP performance? Sorry for bad english.Thank you
 

gordo

Well-known member
Image a linear, already screened bitmap (so curves cannot be applied) step wedge (1. 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 96, 97, 98, 99, 100) at whatever FM screen you want to print with onto your plate. Process the plate. Then, examine the plate and look closely at the dots on the plate. Are they all there? do they look like the dots in the bitmap?
If the dots are all there and look like the bitmap then your problem is probably with the curve you're using.
If the dots are not all there or don't look like the bitmap then your problem is probably with the CtP, plate, or processing.
 

SteveSuffRIT

Well-known member
At 2,400 spi addressability, a single spot is 0.0042" or 10.6um (microns).
How does the single spot look with a "raw" or 'linear" plate, without any curves?
 

gordo

Well-known member
At 2,400 spi addressability, a single spot is 0.0042" or 10.6um (microns).
How does the single spot look with a "raw" or 'linear" plate, without any curves?

How would the OP image a single spot?
How does imaging a single spot relate to the 30 micron FM screen he seems to be using?
 

SteveSuffRIT

Well-known member
Most printers include a QC plate "wedge" in the plate bend margin that contains a 1x1 pixel patch.
If you can image the 1x1 pixel at 10.6um, you can image anything larger, 20, 30 um.
 

Hagar_uk

Member
Our prinect calibration manager create process calibration for 20 microns but I put 30 microns to used it printing on uncoated stock
Norminal 5,10,20,30,40,50,60,70,80,90,95
Process 11.6 / 22.2/ 40.9 / 55.7 / 68 / 77.3 / 84.7 / 90 / 94.3 / 97.4 / 98.8
Measured = same as process
problem is highlight dot always lost look like rubber delete pencil images on notes. Is it come from plate curves or CTP performance? Sorry for bad english.Thank you

Some thoughts on this.

What kind of plates are you using, not all plates/CTP/processors are rated for FM screening.
When you say the highlight dot is bad, is that on plate or press? Where as AM screening is often done with a just a plate linearisation, FM is a different ball game, and needs press curves to be anywhere near close.

Looking at the CTP side, with FM and high LPI it is critical that the focus is the best it can be. If it is out the power the can spread, causing a softdot, which does not fully form, or spreads on postive working plates causing a filling in effect. Having the correct power on plate can sometimes cause similar issues on plate types, The results of too much or too little power will depend on if you sare using posi or neg working plates. Not sure how good the power sensors in the machine are now, but years a go did see a few issues on the crons where they had to sometime be swopped out.
 

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