R&D, It's nothing wrong with your CTP the problem is either plates being stored in excessive humidity or more likely the processor. I would suggest you do the following:
- first thing cut two large plates square to give 800 by 800 mm, put your processor in dumb mode, feed them in your recorder engine with the same orientation to expose a test pattern ideally fullsize 50 percent raster. Allow the first plate to pass into the proc then stop and rotate the second plate 90 deg then feed into proc. This will tell you more about uniformity issues i.e. is it left to right on both plates or not.
- next, dump the chemistry and confirm your FLP machine is properly, mean properly adjusted:
a) check pressure on EACH AND EVERY roller adjustable bearing, put rollers back. I know it's time consuming and silly but incredibly important, and usually overlooked;
b) take out the prewash brush and ajust it properly according to spec;
c) carefully inspect both dev brushes for integrity/wear then adjust thems to spec, if too worn out replace without hesitation. They won't last for more than 14...18 months anyway;
d) check both mixing spraybars inside the dev section to blow on all holes and rotate them as necesary towards the brushes to give a visibly strong flow of liquid when in use;
e) put dev back in, confirm preheat temp on back of plates for all three zones. Check also the two preheat blower fans are working, confirm the temp on all zones is stable at all times, at set values give or take 1 deg. maximum, they should be dead on;
f) bypass interlocks and visually check the plate travel into the FLP as it passes different sections, no hard spots/plate sticking because of excessive pressure somewhere, no funny noises from the drive system, dev mixing properly etc.
Now test for uniformity again, it should come out max. 2...3 percent inconsistency, all corners vs. center of plate. If not, blame the dev brushes first, not the recorder.
If you really think excessive humidity to be an issue it's enough to leave a box flat open or just a few plates stacked vertically somewhere in the ctp room and turn your AC on at full blow set for 21 deg C, allow for 3 hours or so. Provided the PVA hasn't been damaged completely the damp coating will regain its properties gradually in these circumstances perhaps a bit of sensitivity is lost, requiring extra laser intensity but spots will be gone. Done that once with strange patterns on plates coming out from the proc like dalmatian was clearly a humidity prob.
Good luck and come back with results !
