Advice on characteristic curves

Hi all just after some advice on characteristic curves at the start of a job we pre-ink the ink profile and after running say 400-500 sheets the color creeps up and up we are constantly bringing color down on the run by sweep, or profile, it gets to the stage where we calculate how much we have reduced the sweep % and bring it down at the start of the next job , eg: if we dropped the sweep by 8 next job we start by taking 8 off the new job.

I have no experience with curves , am i correct in saying it increases or decreases the speed of the ink fountain roller ?

We only run four colour process and our running speeds are not less than 14000sph but most jobs are 17000-18000 sph .

Any advice greatly appreciated

Cheers
Dave Ross

 

You alter the curves in the service display on the CP2000. Select a stock type, a colour and for simplicity to start with use the percentage button to increase or decrease the curve slopes......start on say 10% and see what happens, the diodes will change by whatever you require for the next job sent via pre-press and when input. There are more specific alterations you can make to basically adjust the curves within a tight tollerance so the colour stays more consistant.

Regards.

Regards.